Gooey Peanut Butter Monster Cookies: A Spooky Halloween Treat Recipe with Marshmallow Webs

Get ready for some hauntingly good fun in the kitchen with these irresistible Peanut Butter Monster Cookies! This recipe takes a beloved classic – my signature Fluffernutter Cookie – and transforms it into a spooky, adorable, and utterly delicious Halloween delight. Whether you’re planning a Halloween party, looking for a festive baking project with the kids, or simply craving something sweet with a twist, these monster cookies are guaranteed to be a hit.

What makes them monstrously good? A playful combination of colorful Halloween candies, a rich peanut butter base, and a surprise gooey marshmallow center. The real magic, however, comes from the final decorative touches. All you need are some whimsical candy eyeballs and a handful of marshmallows to create eerie spider webs or charming mummy wraps draped over each cookie. These details not only make them incredibly festive but also add an extra layer of soft, chewy sweetness that perfectly complements the rich cookie.

Freshly baked Peanut Butter Monster Cookies adorned with melted marshmallow spider webs and fun monster candy eyes, perfect for Halloween.

Now, I’ll be honest with you – working with melted marshmallows for the web effect can get a little sticky. It’s definitely a moment that might test your patience! But I’m here to tell you: take a deep breath, embrace the glorious mess, and know that the result is absolutely worth it. Preparing yourself mentally for a bit of sticky fun transforms a potentially frustrating step into an enjoyable part of the baking process. Think of it as part of the creative monster-making adventure!

These cookies aren’t just a treat for the taste buds; they’re a treat for the eyes and a fantastic activity for the whole family. The combination of salty peanut butter, sweet candies, and gooey marshmallow is simply divine, creating a texture and flavor profile that’s uniquely satisfying. So, gather your ingredients, unleash your inner baker, and get ready to create some monstrously delicious memories this Halloween season!

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Gather Your Monstrous Ingredients

While the ingredient list for these Peanut Butter Monster Cookies might appear extensive at first glance, don’t be intimidated! Many of the additions are purely for fun and festive flair, adding very little to the overall preparation time of the actual cookies. Each component plays a crucial role in achieving that perfect balance of flavor, texture, and spooky appeal that makes these cookies so special.

Beyond the classic cookie base, the stars of our Halloween transformation are the vibrant M&M’s, the unmistakable Reese’s Pieces candy, and, of course, the adorable candy eyeballs that bring our monsters to life. The truly unique addition is the use of extra marshmallows to create those iconic spider webs or eerie mummy wraps. This step adds a wonderful textural contrast and an undeniable visual impact. And when it comes to the marshmallows for melting, don’t stress about their size; whether you use large or mini, they’ll all melt down beautifully to achieve that perfect stretchy consistency for decorating.

Let’s dive into what you’ll need to create these peanut butter delights. You’ll find a blend of pantry staples and special holiday touches that come together to form a truly unforgettable cookie experience. Each ingredient is carefully chosen to contribute to the rich flavor and delightful texture.

A collection of ingredients laid out, ready to be used for making Peanut Butter Monster Cookies, including peanut butter, candies, and marshmallows.

What you need:

Crunchy Peanut Butter (for texture and flavor)
Unsalted Butter (softened for optimal creaming)
Brown Sugar (adds moisture and a caramel-like depth)
Granulated Sugar (for sweetness and crisp edges)
Egg (room temperature, for binding and richness)
Vanilla Extract (enhances all the sweet flavors)
Kosher Salt (balances sweetness and brings out flavor)
All-Purpose Flour (the structural backbone of the cookie)
Quick Cooking Oats (adds chewiness and a wholesome texture)
Baking Soda (for lift and spread)
Whole Milk (adds moisture and helps activate baking soda)
Reese’s Pieces Candy (for classic peanut butter and chocolate flavor)
Halloween M&M Candy (adds festive colors and chocolatey goodness)
Marshmallow Fluff/Cream (the secret to a gooey center)
Flakey Sea Salt (for a gourmet finish and flavor contrast)
Candy Eyeball Sprinkles (for the monster effect)
Marshmallows (for melting into spooky webs)

For precise quantities and detailed instructions, please refer to the comprehensive recipe card located at the bottom of this post.

Use the JUMP TO RECIPE button at the top of the post, or scroll directly to the bottom of the post to see the full recipe card with ingredient measurements and step-by-step instructions.

Crafting Your Spooky Peanut Butter Monster Cookies

Creating these delightful Peanut Butter Monster Cookies is an enjoyable process, starting with a classic cookie-making foundation and building up to the festive Halloween decorations. Each step is designed to ensure a perfect balance of texture, flavor, and visual appeal, leading to a cookie that’s both delicious and fun to look at.

Building the Perfect Cookie Base

The journey to the perfect monster cookie begins just like my classic Fluffernutter – by thoroughly blending the softened butter and both types of sugar. This creaming process is crucial; you want to beat them together until the mixture becomes wonderfully light, fluffy, and visibly pale. This incorporates air, which is essential for a tender, chewy cookie texture. Following this, the egg, vanilla extract, and whole milk are added and beaten in, ensuring a smooth, cohesive wet mixture that will bind our cookie dough beautifully.

Softened butters and sugars placed in the bowl of a stand mixer, ready for creaming.

Butters and sugars in the stand mixer bowl after being perfectly creamed into a light and fluffy consistency.

Mixing and Filling for Gooey Centers

Next, the dry ingredients – all-purpose flour, quick cooking oats, and baking soda – are gently stirred into the wet mixture until just combined. Overmixing at this stage can lead to tough cookies, so be mindful. The grand finale for the dough is folding in the festive Halloween M&M’s and Reese’s Pieces candy. These not only add bursts of color but also rich chocolate and peanut butter flavors, enhancing the overall monster theme.

Once your dough is ready, it’s time for the signature marshmallow fluff filling. Portion out the dough, flatten each piece, and pipe about two tablespoons of marshmallow fluff into the center. Carefully fold the dough around the fluff, encasing it completely, and then gently flatten the stuffed cookie dough balls once more. This technique ensures that each cookie bakes with a gloriously gooey, melted marshmallow surprise in its heart, setting these monster cookies apart.

Adding all-purpose flour and quick cooking oats to the creamed butter and sugar mixture.

Gently folding in festive Halloween M&M candy and Reese's Pieces candy into the cookie dough.

Baking, Cooling, and Monstrous Decoration

After baking to golden perfection, allow the cookies to cool slightly. The real fun begins with the marshmallow webbing. Melt your marshmallows in a microwave-safe bowl – choose one much larger than you think you’ll need, as marshmallows expand significantly! Heat in short bursts (30-45 seconds initially, then 15-second increments) and stir until smooth and incredibly stretchy. This is where the magic happens, and yes, it gets wonderfully messy.

As mentioned earlier, approach this step with a calm and playful mindset. It’s a fun mess, and a little warm water will clean your hands right up. The trick is to work with small amounts of melted marshmallow at a time, stretching it between your fingers to create delicate, wispy strands that mimic spider webs or mummy wraps. Drape these over your cooled cookies, letting the sticky strands cling to the surface. It’s an artistic process, and no two monster cookies will look exactly alike, which only adds to their charm.

Marshmallows melting in a bowl, preparing for the stretchy spider web decoration.

Hands stretching gooey marshmallow over cookies to create realistic spider web or mummy wrap effects.

Once your cookies are artfully webbed or wrapped, it’s time for the final, most charming touch: adding the candy eyeballs! There’s no right or wrong way to do this. You can add one large eye for a cyclops monster, two for a traditional look, or even three or four for a truly creepy-crawly effect. The more eyes, the scarier (and funnier!) I say! These edible eyes instantly bring personality to your cookies, transforming them from mere treats into characterful Halloween creations.

Finished Peanut Butter Monster Cookies, fresh from the oven, featuring delicate marshmallow webs and an array of candy monster eyes, ready for a Halloween celebration.

Expert Tips & Tricks for Perfect Monster Cookies

Achieving bakery-quality Peanut Butter Monster Cookies is easier than you think with these expert tips and tricks. From perfecting the dough to mastering the marshmallow webs, these insights will help you create cookies that are not only delicious but also visually stunning.

Creaming is Key: Don’t rush the creaming process. Beat the butters and sugars together for a solid 3-4 minutes. You’ll notice the mixture becoming significantly lighter in color and fluffier in texture. This aeration is vital for tender, chewy cookies that spread perfectly.
Precise Marshmallow Filling: For a consistently gooey center, after portioning your dough, gently flatten each of the 12 portions using your three center fingers to create a shallow cup. Transfer your marshmallow cream into a piping bag (or a zip-top bag with the corner snipped) and pipe approximately 2 tablespoons into the center of each flattened cookie dough disc. Carefully wrap the dough around the marshmallow cream, completely encasing it, then gently flatten the filled ball again before placing it on the baking sheet. This method ensures a beautiful, even cookie that’s neither too flat nor too tall.
The Magic of Flakey Sea Salt: Immediately after taking the cookies out of the oven, while they are still warm, sprinkle them generously with a high-quality flakey sea salt, such as Maldon or Nordur. This simple step is a game-changer! The salt not only adds a delightful crunch but also brilliantly cuts through the sweetness of the cookie and the marshmallow cream, elevating the flavor profile and making each bite even more enjoyable.
Bakery-Style Candy Topping: To achieve that appealing “bakery look,” reserve a portion of your M&M’s and Reese’s Pieces candy. As soon as the cookies emerge from the oven, gently press these reserved candies onto the warm tops. This ensures that vibrant colors and distinct shapes are prominent, giving your monster cookies a professional and irresistible finish that simply mixing candies into the dough can’t fully achieve.
Melting Marshmallows for Webs: When melting marshmallows for the spooky web effect, use a microwave and heat them in 15-second increments. Stir thoroughly after each increment until they are fully melted, smooth, and very stretchy. In my experience, about 45 seconds is often sufficient, but microwaves vary, so watch them closely. The goal is a gooey, stringy consistency that can be stretched into fine strands.
Patience with Marshmallow Stretching: This step requires patience and a playful attitude. The melted marshmallow is very sticky, so the best tip is to work with small amounts at a time. Pick up a small glob with 2 or 3 fingers, then gently stretch it between your hands to create thin, web-like strands. Drape these strands over the cookies, brushing the marshmallow off your fingers onto the cookie edges to get it to stick. Work slowly and embrace the mess – a little warm water is all you need for easy cleanup!
Storage & Freezing: These delicious baked Peanut Butter Monster Cookies can be stored in an airtight container at room temperature for up to 5 days, maintaining their freshness and chewiness. If you’re planning ahead or have leftovers (though I doubt you will!), they also freeze beautifully. To freeze, first place the cooled cookies in a single layer on a baking tray and freeze until solid. Once frozen, transfer them to a zip-top freezer bag or an airtight container, and they will keep well for up to 3 months. Thaw at room temperature before serving for the best texture.

Smart Substitutions for Your Monster Cookies

Flexibility in baking can be a lifesaver, and this Peanut Butter Monster Cookies recipe is quite adaptable. Here are some smart substitutions you can make without compromising too much on flavor or texture, ensuring you can bake these spooky treats no matter what you have on hand.

Peanut Butter Preference: My personal preference is crunchy peanut butter because it adds fantastic texture and extra nutty flavor to the cookies. However, if you only have smooth peanut butter on hand, it will work perfectly fine. The texture won’t be identical, but the inherent peanut butter flavor will still shine through, especially since you’ll be adding other whole candies later.
Butter Type: This recipe calls for unsalted butter, allowing for precise control over the salt content. If you find yourself with only salted butter, simply omit the ½ teaspoon of kosher salt from the ingredient list. This adjustment will prevent your cookies from becoming too salty.
Sugar Choices: Light brown sugar is generally preferred for its milder molasses flavor and softer texture contribution. However, dark brown sugar can be used in a pinch. Be aware that using dark brown sugar will result in cookies with a slightly deeper, richer color and a more pronounced molasses flavor. It’s not a bad thing, just a subtle shift in the cookie’s character.
Gluten-Free Option: For those with gluten sensitivities or preferences, these cookies can be effortlessly made gluten-free. Simply swap the all-purpose flour for a high-quality cup-for-cup gluten-free baking flour blend. The cookies will bake up beautifully with a texture very similar to their gluten-containing counterparts.
Candy Customization: I love the vibrant mix of Halloween M&M’s and Reese’s Pieces for their combined chocolate and peanut butter punch, perfectly aligning with the cookie’s base. However, feel free to customize your candy additions! You can use all of one kind if you prefer, or even mix in other small, sturdy candies. But honestly, who could resist more chocolate and peanut butter in one bite, especially for a monster cookie?
Marshmallow Fluff vs. Cream: The recipe specifically calls for marshmallow fluff, but you might encounter other brands labeling it as marshmallow cream, marshmallow paste, or marshmallow spread. Rest assured, these are essentially the same product and are interchangeable for this recipe. They all provide that unique, sweet, gooey center that makes these cookies so special.
Mini Marshmallows for Filling (Use with Caution): While you might be tempted to use mini marshmallows as a substitute for marshmallow fluff in the cookie filling, I strongly advise against it. While technically possible, the texture and final result simply won’t be the same. Marshmallow fluff provides a smoother, more consistent, and intensely gooey center that mini marshmallows just can’t replicate. Stick with the fluff or cream for the best results in the center.
Mini Marshmallows for Decorating (Perfect!): The *only* time and place I recommend using mini marshmallows in this recipe is for melting down to create the stretchy spider webs or mummy wraps. Their smaller size makes them melt faster and more evenly for this specific decorative purpose.

A close-up of Peanut Butter Monster Cookies with marshmallow webs and candy eyes, showcasing their detailed and festive Halloween design.

More of My Favorite Fall Treats to Enjoy

If these Peanut Butter Monster Cookies have captured your heart and taste buds, you’re in for a treat! Fall is a season brimming with cozy flavors and festive baking, and I have plenty more recipes to help you celebrate. From unique twists on classics to comforting staples, here are some other fall favorites you won’t want to miss:

Candy Corn Fluffernutters: If you adored the base of these Monster Cookies, you absolutely must try my other favorite fall version: Candy Corn Fluffernutters. These colorful cookies are also based on the beloved original recipe that I proudly baked for Joanna Gaines in the prestigious Silos Baking Competition. They’re a vibrant and sweet celebration of a classic Halloween candy!
Ultimate Candy Corn and Peanuts Fall Snack Mix: Whether you’re a devoted fan of candy corn or just enjoy a sweet and salty snack, my Ultimate Candy Corn and Peanuts Snack Mix is perfect for Halloween night. It’s an addictive blend of flavors and textures, ideal for munching while you hand out candy or settle in for a spooky movie night.
Starbucks-Style Pumpkin Spice Bread: While it might not be “scary” in a Halloween sense, it’s scary good! All throughout the fall season, I love to bake this incredibly moist and fragrant Pumpkin Spice Bread. It tastes just like your favorite coffee shop’s version (yes, Starbucks!), but even better because it’s baked fresh right in YOUR oven. The aroma alone is enough to get you in the fall spirit!

I hope these additional fall treats bring even more joy and deliciousness to your autumn celebrations. Happy baking!

Did you make this recipe and love it? Let me know by leaving a review or comment below! Your feedback means the world. And don’t forget to sign up for my newsletter to get delicious recipes delivered straight to your inbox. You can also follow along on Instagram, Pinterest, and Facebook for more baking inspiration and behind-the-scenes fun!

📖 Recipe

Yield: 12 large cookies

Peanut Butter Monster Cookies

Prep Time:
15 minutes

Cook Time:
20 minutes

Total Time:
35 minutes

This recipe for Peanut Butter Monster Cookies takes my classic Fluffernutter Cookie and gives them a spooky Halloween twist.

Ingredients

¾ cup Crunchy Peanut Butter, not natural
8 tablespoons Unsalted Butter, soft
½ cup Brown Sugar
½ cup Granulated Sugar
1 Egg, room temp
1 tablespoon Vanilla Extract
½ teaspoon Kosher Salt
1 ½ cups All-Purpose Flour
½ cup Quick Cooking Oats
1 teaspoon Baking Soda
1 tablespoon Whole Milk
½ cup Reeses Pieces Candy
½ cup Halloween M&M Candy
½-1 cup Marshmallow Fluff/Cream
Flakey Sea Salt, like Maldon or Nordur
Candy Eyeball Sprinkles, for topping
5 large Marshmallows (or 1 cup mini), for making spider webs

Instructions

Preheat oven to 350˚F and prepare 3 half baking sheets by lining them with parchment paper.

In the bowl of a stand mixer fitted with the paddle attachment, combine butter, peanut butter, and both sugars. Cream together, scraping down at least twice, until everything is evenly combined. 4 minutes

Add the egg and vanilla, and beat until well combined. 45-60 seconds longer.

Add salt, flour, oats, baking soda, and milk, and mix at low speed until flour is completely worked in. Whack the mixer up to full speed and then off, quickly, for a final mix. 2 seconds.

Fold in the Reeses pieces and M&M’s.

Use a 2-ounce scoop to scoop cookies onto a parchment-lined cookie sheet. I use a small ice cream scoop for equal-sized cookies. You should get 12 extra large cookies.

Flatten the cookies with your hands, add about 2 tablespoons of fluff, and fold the cookie up around the fluff, encasing it in the cookie dough. Flatten them just a little, again, once filled, and place them 3-4 inches apart on your parchment-lined trays. Only 4 cookies per sheet, they get BIG!

Bake in the preheated oven for 16-18 minutes, just until the top and edges begin to turn golden brown and they have split and the marshmallow begins to show.

Remove from the oven and tap gently on the stove or counter. Sprinkle them with the flakey salt and top each cookie with as many candy eyeballs as you desire to make your cookies spooky.

Let the cookies cool on the pan for about 5 minutes so the fluff can set. Then transfer them to a cooling rack until completely cool.

Finally, microwave the marshmallows in 15-second increments until they are gooey and stretchy. Stir them till you see strands begin to appear.

Let them cool till you can touch them but still warm, then pick up a glob of them with your hands, stretch them to look like spider webs, and drape them onto the cookies. It gets a little messy but adds a spooky element to the final cookie.

Notes

NOTES & TIPS

Be sure to cream the butters and sugars together for 3-4 minutes, you will see the mixture change to a lighter color. When it gets pale you have beat in enough air.

After you have made your cookie dough, portion it out and flatten each of the 12 portions using your 3 center fingers. Place the marshmallow cream in a piping bag, then cut off the tip and pipe about 2 tablespoons into the center of each cookie. Wrap the cream in the dough, then flatten again before baking. This gives a very consistent and not too flat, not too tall cookie.

When the cookies come out of the oven. Immediately sprinkle them with some flakey sea salt, it helps cut the sweetness of the cookie and the marshmallow cream and makes them even more enjoyable!

I also reserve some candy for pressing into the top after they come out of the oven too. This gives that bakery look that you don’t get from ONLY mixing the candy into the cookie dough.

Melt the marshmallows for stretching over the top in 15-second increments in the microwave until melted. Mine only took 45 seconds. Stir after each time in the microwave until stretchy.

Now is the time to exercise patience. The marshmallow stretching is messy. The best tip I have for you is, the less you work with at a time, the better. Use a small bit and stretch between 2 or 3 fingers and then press it over the cookies, brushing the marshmallow off onto the edges of the cookie to get it off your hands and to stick to the cookies.

Work slowly, and know it is a bit crazy, but if you get in the right mindset and have fun with it, the mess can be cleaned up with a little warm water.

Baked Fluffernutter Cookies can be kept in an air-tight container for up to 5 days at room temperature. And while mine would never make it there, they can be frozen for up to 3 months. Freeze them flat on a tray, then transfer them to a zip-top freezer bag.

SUBSTITUTIONS

My favorite peanut butter is crunchy! But you can use smooth in a pinch if you need to. There are whole peanuts going in later anyway.

If you have to use salted butter because that is all you have on hand, remove the addition of salt later in the recipe.

Light brown sugar is preferred for this recipe, however, you can use dark in a pinch. The cookies will just have a little deeper color and molasses flavor to them. Which isn’t bad, just a little richer.

These cookies bake up beautifully and can be made gluten-free when you use THIS cup-for-cup baking flour swap.

I used a mix of Halloween M&M’s and Reese’s pieces candy for my cookies. You can use all of one kind if you prefer, but who doesn’t want more chocolate and peanut butter?

While I prefer the original marshmallow fluff, you may also find other brands out there calling it marshmallow cream, they are essentially the same and you can use either for this cookie. You may also encounter it called marshmallow paste or spread.

While you might be tempted to use mini marshmallows in place of the “fluff” and it could work, the texture and end result just aren’t the same. You CAN do it, but I’d heavily suggest using the marshmallow cream.

The time and place for the mini marshmallows is for melting to make the spider webs/mummy wraps, whichever you prefer to say they look like.

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