Soft, chewy peanut butter bars with a gooey marshmallow layer. If you enjoy the classic sandwich or the sweet-and-salty combo, these fluffernutter bars are for you.
I’ve never been tempted by eating a fluffernutter sandwich made with two slices of white bread—the idea seems sticky—but I do love the flavor pairing in baked treats. Peanut butter and marshmallow fluff are easy to balance in desserts, letting you customize sweetness while enjoying that addictive salty-sweet contrast.
These fluffernutter bars showcase the combination perfectly. The base is a soft, chewy peanut butter blondie with plenty of peanut flavor but not too sweet. A full jar of marshmallow fluff becomes a gooey middle layer, while a reserved portion of the peanut butter dough is pinched and scattered on top before a short final bake.
In short, the marshmallow filling is surrounded by a tender, peanut-buttery blondie.
To start, make the peanut butter dough that acts as both base and topping. I kept the blondie base from becoming overly sweet because the marshmallow layer provides plenty of sweetness on its own. The bars stay soft and chewy thanks to the right amount of flour—measure carefully by spooning the flour into the cup and leveling it off so the bars don’t dry out.
Reserve about 1 cup of the peanut butter batter; press the remainder into a 9×13-inch pan to form an even layer. Bake that base for roughly 20–25 minutes, until the top is set.
Next, spread the entire jar (7 oz) of marshmallow fluff over the baked peanut butter layer. This is the stickiest step, since marshmallow fluff clings easily. If you prefer extra goo, you can use more than one jar, but one jar strikes a good balance: gooey without being overwhelmingly sweet or messy.
Pinch off pieces of the reserved peanut butter dough, flatten each slightly into roughly 1-inch pieces, and scatter them over the marshmallow—no need to cover completely; I cover about 80–90%. Return the pan to the oven and bake about 10 minutes more, until the peanut butter pieces no longer look doughy. If your oven allows, turn off the top heating element to prevent any marshmallow peaks from browning too much.
Pro Tip: Let the bars cool at least one hour before slicing. Use the parchment overhang to lift the slab from the pan onto a cutting board. Lightly spray a sharp knife with non-stick cooking spray if you like—the blade will glide more easily through the marshmallow without dragging.
The finished bars are soft, chewy, and perfectly gooey, balancing salty peanut butter with sweet marshmallow in every bite.
Fluffernutter Bars
30
35
1 5
15 bars
Equipment
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9×13 Inch Pan
Ingredients
- 2 1/4 cups all-purpose flour
- 1 teaspoon baking powder
- 1/4 teaspoon salt
- 3/4 cup unsalted butter, softened
- 3/4 cup brown sugar
- 1/3 cup white sugar
- 1 1/2 cups smooth peanut butter*
- 1 large egg
- 1 large egg yolk, in addition to the other egg, discard the white
- 7 oz jar marshmallow fluff
Instructions
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Preheat the oven to 350°F and position the rack in the middle.
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Line a 9×13-inch pan with parchment paper, leaving an overhang, or line with foil and lightly grease.
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Whisk the flour, baking powder, and salt in a medium bowl.
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In a large bowl, beat together the softened butter, brown sugar, and white sugar until soft and combined.
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Beat in the peanut butter, then add the egg and egg yolk and mix until smooth.
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With the mixer on low, add the flour mixture gradually, about half at a time, until just combined.
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Remove about 1 cup of batter and set aside.
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Press the remaining dough into the bottom of the prepared pan in an even layer.
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Bake the base for 25 minutes, or until the top is fully set.
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Remove the pan from the oven and spread the jar of marshmallow fluff evenly over the baked layer.
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Pinch pieces of the reserved dough into roughly 1-inch flattened pieces and scatter over the marshmallow layer, covering about 80–90%.
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Return to the oven and bake 10 minutes more, until the top peanut butter pieces are set.
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Let the bars cool at room temperature at least 1 hour before slicing.
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Use the parchment overhang to lift the slab onto a cutting board. Lightly grease a thin, sharp knife with cooking spray to prevent sticking and slice into bars.
Notes
- Do not use natural or homemade peanut butter that separates easily; use a stable, commercial smooth peanut butter. For crunchy peanut butter, increase to 1 3/4 cups.
- A metal pan yields crisper edges, while a glass pan produces slightly softer edges.
- Store bars in an airtight container at room temperature for up to 5 days.
- Nutrition values are estimates based on 15 bars and are for reference only.
Nutrition
Carbohydrates: 46g,
Protein: 9g,
Fat: 23g