Fluffernutter Brownies are Pure Nostalgia

A classic, fudgy chocolate brownie recipe topped with pretty swirls of peanut butter and marshmallow fluff makes the perfect fluffernutter brownie. They’re a bake sale hit!

Fluffernutter Brownies are Pure Nostalgia
Close-up: fluffernutter brownie cut into squares on a piece of parchment paper
Simply Recipes / Annika Panikker

These fluffernutter brownies have a reputation that goes back over a decade. When I was a kid, my school had an annual charity festival that included bake sales, music, games, and all sorts of fun activities put on by the students. Every year, I contributed to the bake sale. Fluffernutter brownies were always the first item to sell out, and they became my signature recipe. I have been making them ever since. 

As a kid, I absolutely loved a toasted fluffernutter sandwich, and my obsession with a classic indulgent chocolate brownie goes way back. This recipe pairs a bittersweet chocolate brownie with salty, nutty peanut butter and sweet and chewy marshmallow fluff. The flavors and textures of fluffernutter brownies are satisfying in every single bite. 

My fluffernutter brownies take less than an hour to make start to finish, making them an easy sweet treat to bake during the week. But be warned: you need real patience to let them cool down completely before slicing—otherwise, you won’t get neat, clean cuts. 

Using a Boxed Brownie Mix

This is a decadent chocolate brownie recipe that uses melted chocolate and cocoa powder to enhance that flavor. Instead of making it from scratch, you can use a boxed brownie mix as a shortcut. This recipe works well with a fudge brownie or a cake brownie mix, prepared according to the package. 

Fluffernutter brownie cut into squares on a piece of parchment paper
Simply Recipes / Annika Panikker

Let’s Talk Peanut Butter

Most store-bought peanut butters are a spreadable consistency, and to achieve those whimsical swirls we need the peanut butter to be runny. Warm up the peanut butter in the microwave for 20 to 30 seconds and stir well before dolloping over the brownie batter and swirling. You can also use room-temperature natural peanut butter, which is naturally runny.

If you have a peanut allergy, you can swap the peanut butter for almond butter, tahini, or sunflower seed butter. Whichever nut/seed butter you choose, make sure they are creamy and runny in consistency before using. 

Tips for the Perfect Fluffernutter Brownie

  • Beat the eggs and sugars until pale and creamy. This ensures a crunchy top on the brownies once baked.
  • Fold the dry ingredients into the wet ingredients gently, as we don’t want to knock out all that air from the egg mixture.
  • Don't over-swirl the peanut butter and marshmallow fluff into the brownie batter or else you will lose the distinct, pretty pattern.
  • For clean edges, don’t slice the brownies until they have completely cooled down.
Stack of fluffernutter brownies on a small piece of parchment paper
Simply Recipes / Annika Panikker

More Brownie Deliciousness

Preheat the oven to 350°F.

Spray an 8x8-inch square pan with baking spray and line with parchment paper.

Melt the butter and chocolate:

In a small microwave-safe bowl, add the butter and chocolate and heat it in the microwave for 20-second intervals, stirring each time, just until melted and smooth. Set aside to cool a bit.

Bowl of chocolate and butter pieces, and next to the bowl, a spatula resting on a small plate and a blue and white kitchen towel for fluffernutter brownie recipe
Simply Recipes / Annika Panikker
Bowl of melted chocolate and butter, , and next to the bowl, a spatula resting on a small plate and a blue and white kitchen towel for fluffernutter brownie recipe
Simply Recipes / Annika Panikker

Beat the eggs and sugar:

In a mixing bowl, add the eggs, granulated sugar, and brown sugar and beat with a whisk until pale and fluffy, about 4 minutes. Alternatively, you can use an electric beater and meat on medium speed for about 2 minutes. 

Bowl of brown sugar and eggs, and next to the bowl, a spatula resting on a small plate and a blue and white kitchen towel for fluffernutter brownie recipe
Simply Recipes / Annika Panikker
Brown sugar and eggs after whisked together until light and fluffy, and next to the bowl, a whisk resting on a small plate and a blue and white kitchen towel for fluffernutter brownie recipe
Simply Recipes / Annika Panikker

Assemble the brownie batter:

Add the melted butter and chocolate mixture to the beaten eggs and gently fold together until combined. 

Sift the flour, cocoa powder, and salt over the chocolate mixture. Fold the dry ingredients into the wet. Be gentle and do not overwork the batter.

Fluffernutter brownie wet ingredients in a bowl after whisked togther, and next to the bowl, the whisk resting on a small plate and a blue and white kitchen towel
Simply Recipes / Annika Panikker
Dry ingredients carefully folded into the wet ingredients using a spatula, all next to a small plate and a blue and white striped kitchen towel for fluffernutter brownies recipe
Simply Recipes / Annika Panikker
Fluffernutter brownie batter in a bowl next to a small plate with the spatula and a blue and white striped kitchen towel
Simply Recipes / Annika Panikker

Add to the baking pan and make the swirl:

Transfer the brownie batter to the lined pan and smooth out the top. 

Make sure the peanut butter is runny (you can pop it in the microwave for 20 seconds and stir well if it's too stiff). 

Use a spoon to dollop the peanut butter and marshmallow fluff on top of the brownie batter in equal intervals. Drag a butter knife through the dollops to swirl it around. Do not over-swirl it as you want distinctive peanut butter and marshmallow swirls once baked.

Fluffernutter brownie butter spread evenly into the baking pan, and next to it, the blue and white striped kitchen towel
Simply Recipes / Annika Panikker
Small dollops of peanut butter and marshmallow fluff added to fluffernutter brownie butter in the baking pan, and next to it, the blue and white striped kitchen towel
Simply Recipes / Annika Panikker
Peanut butter and marshmallow fluff swirled into fluffernutter brownie butter in the baking pan, and next to it, the blue and white striped kitchen towel
Simply Recipes / Annika Panikker

Bake:

Bake until the top is set and a toothpick inserted into the center comes out with very moist (but not raw liquid) batter attached, 35 to 45 minutes.

Baked fluffernutter brownie in the baking pan and next to it, the blue and white striped kitchen towel and a blue and white striped pot holder
Simply Recipes / Annika Panikker

Cool and slice:

Let cool completely before cutting into squares and serving with a glass of milk. 

Store leftover fluffernutter brownies at room temperature for up to 3 days or in the fridge for up to a week. 

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Fluffernutter brownie cut into 16 slices on a piece of parchment paper, and in the surroundings, a white kitchen towel, forks on the counter, a stack of small plates, and a glass of milk
Simply Recipes / Annika Panikker
Close-up: fluffernutter brownie slices close together with the middle piece turned on its side to showcase cross section
Simply Recipes / Annika Panikker