Fluffernutter Brownies

Creamy, sticky, sweet marshmallow crème swirled with salty, nutty, rich peanut butter tops a dense, fudgy brownie studded with chocolate and peanut butter chips – and sandwiching a layer of peanut butter cup candy. If you grew up with fluffernutter sandwiches, the inspiration is instantly recognizable. If you’re new to the marshmallow‑and‑peanut‑butter pairing, I suspect this recipe will convert you on the first bite.

A Fluffernutter Brownie on a small plate displaying distinct layers


As I mentioned in my Marshmallow Crème post, fluffernutter sandwiches were a lunchtime staple in our house. My sister, in particular, went through a phase where she requested a “peanut butter fluff” sandwich Every. Single. Day. She has since done a full 180°, refusing to touch anything with peanut butter as an adult. While I suppose it’s possible to overindulge in a flavor combination, this is one that never gets old for me.

I first started making these brownies in 2019. They were one of several county fair entries that year – while not my top performer, they did bring home a third‑place ribbon. Back then, the topping was nearly the same height as the brownie layer and was made with a softer set version of a traditional marshmallow rather than a crème. The peanut butter was buried underneath, both literally and in terms of flavor – in short, the balance was off. What makes fluffernutters so special is the harmony of salty and sweet, not one overwhelming the other.

Since I perfected my homemade marshmallow crème, I decided it was time to dust off this recipe and give it a thoughtful makeover. I made a few updates to the brownie batter to bring it closer to my current style, but the real transformation is in the topping. I reined in the proportions so the marshmallow sits more like a generous frosting, complimenting rather than overpowering the brownie, and swirled a thick ribbon of smooth peanut butter right across the top. Now, the inspiration is unmistakable at a glance and evident in every salty-sweet bite.

Who knows – maybe these are finally worthy of first place instead of third. If you give them a try, let me know how they stack up.

A Fluffernutter Brownie on a small plate displaying distinct layers

Fluffernutter Brownies

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A fudgy, gooey, peanut-buttery, layered brownie inspired by New England's favorite childhood sandwich.
Prep Time 25 minutes
Cook Time 35 minutes
Resting Time 2 hours
Total Time 3 hours
Servings: 40
Course: Dessert
Cuisine: American
Baking Ambition: Adventurous
Calories: 232

Equipment

  • baking pan (9" x 13")
  • non-stick foil (heavy duty)
  • mixing bowls
  • As an Amazon Associate I earn from qualifying purchases.kitchen scale (or measuring cups)
  • measuring spoons
  • whisk (or electric mixer with whisk attachment)
  • spatula

Ingredients
 
 

Brownies
  • 100 g flour
  • 30 g peanut butter powder
  • 12 g cocoa powder
  • 6 g salt
  • 340 g chocolate dark, between 50% – 60% cacao
  • 224 g unsalted butter
  • ½ teaspoon espresso powder
  • 5 eggs
  • 200 g sugar
  • 110 g brown sugar
  • 15 ml vanilla
  • 170 g peanut butter chips
  • 85 g milk chocolate chips
  • 209 g Reese's Peanut Butter Cup Thins
  • 256 g peanut butter divided
  • 285 g homemade marshmallow crème

Method
  

Make the brownies:
  1. Pre heat oven to 350°. Line with non-stick foil (or lightly grease), a 9” x 13” brownie or cake pan.
  2. Whisk together the flour, peanut butter powder, cocoa powder and salt in a small bowl. Set aside.
    100 g ( cup) flour, 12 g (2 tbsp) cocoa powder, 6 g (1 tsp) salt, 30 g (2 tbsp) peanut butter powder
  3. Place the dark chocolate, unsalted butter, and espresso powder in a large microwave safe bowl. If your microwave has a chocolate melting feature, use that, otherwise, heat for 1 minute in the microwave, stir and then continue to heat in 30 second bursts, stirring after each, just until the chocolate is fully melted. (This can also be done over a double boiler.)
    340 g (2 cups) chocolate, 224 g (1 cup) unsalted butter, 1/2 teaspoon (½ teaspoon) espresso powder
  4. While the chocolate and butter are melting, whisk the eggs, sugar and brown sugar until thick and ribbony (this is faster with an electric mixer, but can be done by hand). Whisk in the vanilla until combined.
    200 g (1 cup) sugar, 110 g (½ cup) brown sugar, 5 eggs, 15 ml (1 tbsp) vanilla
  5. Whisk the chocolate mixture into the egg mixture until a homogenous, glossy mixture is achieved. At this point the sugar should be fully dissolved with no grittiness in the mixture.
  6. Stir in the flour mixture just until it disappears. Fold in the peanut butter chips and chocolate chips.
    170 g (6 oz) peanut butter chips, 85 g (½ cup) milk chocolate chips
  7. Pour half of the batter into the prepared pan, smooth out the top. Arrange the peanut butter cups evenly over the surface of the batter. Top with the remaining batter, carefully spread to the edges of the pan ensuring all of the peanut butter cups are covered
    209 g (7 ⅜ oz) Reese's Peanut Butter Cup Thins
  8. Pipe, spoon or dollop half of the peanut butter over the surface of the batter. Use a butter knife to gently swirl the peanut butter into the surface of the batter (the knife can only extend very slightly into the batter, you want to avoid disrupting the peanut butter cup layer – the goal is to make sure there are swirls of peanut butter in every bite of brownie)
    128 g (½ cup) peanut butter
  9. Place the pan in the pre-heated oven and bake for about 35 minutes. The top will appear set and glossy around the ribbons of peanut butter, the edges slightly puffed and possibly a crack or two in the surface. Place on a wire rack to cool completely.
  10. Spoon the marshmallow crème over the top of the cooled brownies, spread into an even layer all the way to the edges of the brownies. Pipe, spoon or dollop the remaining peanut butter over the surface of the marshmallow layer. Use a butter knife to gently swirl the peanut butter through the marshmallow layer (avoid hitting/digging into the brownie layer underneath)
    285 g (10 oz) homemade marshmallow crème, 128 g (½ cup) peanut butter
  11. For the cleanest cuts, chill the bars for at least an hour before cutting into 24 large bars, 32 medium bars or 40 small bars. Store in an air-tight container at room temperature.

Notes

  • You can use store bought marshmallow cream for this recipe, but, if you do, you’ll need to store the brownies in the refrigerator to prevent the marshmallow layer from flowing down the sides of the brownies.

Nutrition

Serving: 1brownieCalories: 232kcalCarbohydrates: 27gProtein: 4gFat: 14gSaturated Fat: 6gPolyunsaturated Fat: 1gMonounsaturated Fat: 5gTrans Fat: 0.2gCholesterol: 33mgSodium: 121mgPotassium: 106mgFiber: 1gSugar: 21gVitamin A: 176IUVitamin C: 0.02mgCalcium: 19mgIron: 1mg

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