Fluffernutter Bars

These chewy Fluffernutter Bars feature a rich, salty-sweet peanut butter cookie dough base layered with gooey marshmallow fluff and toasted to absolute perfection.

Why This Recipe Works:

• The extra egg yolk strengthens the protein matrix, preventing the peanut butter fats from separating during the bake.
• Creaming the butter and peanut butter together first encapsulates the oil-soluble flavor compounds, ensuring a rich taste in every bite.
• A strategic dusting of cornstarch over the marshmallow layer prevents it from dissolving into the cookie dough.

I still remember the sticky, humid July afternoon in my mother's kitchen when I tried to bake a giant peanut butter sandwich. I was eight, unsupervised, and convinced that melting marshmallow fluff directly onto white bread in a hot oven would yield culinary genius. Instead, I created a smoking, charred disaster that permanently fused to her favorite baking sheet.

My mother was not amused.

Decades later, my adult attempts at recreating those nostalgic flavors in bar form kept running into the exact same structural roadblock. Standard cookie dough bases are simply too heavy, causing the delicate marshmallow fluff to liquefy and boil over the edges of the pan. I tested this with four different flour ratios, and every single batch ended up as a greasy, separated puddle because the fat in the peanut butter broke down the egg proteins. It was incredibly frustrating to watch beautiful ingredients turn into a sweet, soupy mess.

The simple fix is adjusting the protein matrix of the dough. By adding an extra egg yolk, we create a sturdy barrier that holds the marshmallow.

Trust me on this one, because this technique yields the most spectacular results. You get a deeply caramelized, salty-sweet bar that cuts cleanly without oozing all over your cutting board. If you love the texture of our Iowa State Fair Chewy Cookies, this hybrid creation will absolutely blow your mind.

Fluffernutter Bars

• Publisher Storied Skillet
• Cuisine American
• Category Desserts, Bars
• Prep Time 15 minutes
• Cook Time 25 minutes
• Servings 16
• Calories 280 calories
• Rating 4.8 4288
• Tags fluffernutter bars, peanut butter marshmallow bars, chewy dessert bars

Ingredients

• 115g unsalted butter, softened (½ cup)
• 135g creamy peanut butter (½ cup)
• 150g light brown sugar, packed (¾ cup)
• 1 large egg plus 1 egg yolk, room temperature
• 1 tsp vanilla extract
• 180g all-purpose flour (1 ½ cups)
• ½ tsp baking powder
• ½ tsp Diamond Crystal kosher salt (approx. 1.5g)
• 200g marshmallow fluff (approx. 1 jar)

Directions

1. Preheat your oven to 350°F (175°C) and line an 8x8-inch metal baking pan with parchment paper, leaving an overhang on the sides.
2. In a large bowl, cream together the softened butter, creamy peanut butter, and brown sugar using a hand mixer until light and fluffy.
3. Beat in the egg, egg yolk, and vanilla extract until fully incorporated and smooth.
4. Whisk together the flour, baking powder, and Diamond Crystal kosher salt in a separate bowl, then fold into the wet ingredients until a soft dough forms.
5. Press two-thirds of the dough into the bottom of the prepared pan using the heel of your hand to form an even layer.
6. Spread the marshmallow fluff evenly over the dough base, leaving a small border around the edges.
7. Crumble the remaining cookie dough over the top of the marshmallow layer, pressing down gently.
8. Bake for 23 to 25 minutes until the top is golden brown and the marshmallow is puffed and toasted. Let cool completely before slicing.

Notes

• Use standard commercial peanut butter like Skippy or Jif. Avoid natural, oil-separating brands because the excess free lipids will destroy the dough's structural integrity.
• We use Diamond Crystal kosher salt (½ tsp or 1.5g). If using fine table salt, reduce the amount by half to prevent an overly salty base.
• Keep a close eye on the oven during the last 5 minutes of baking. Marshmallow fluff contains high sugar levels that can transition from beautifully toasted to burnt in a matter of seconds.
• After a day in an airtight container, the marshmallow layer will absorb moisture from the cookie base, making the bars even chewier and softer.
• If you enjoy the gooey texture of our Gooey Smores Cookie Bars, you will love how the marshmallow fluff behaves here.

Serving Suggestions

These bars are incredibly rich, so they pair beautifully with contrasting textures and temperatures. Here are a few ways to serve them:

• Serve warm with a scoop of vanilla bean ice cream to balance the salty-sweet peanut butter.
• Pair with a cold glass of milk or a refreshing Iced Coffee Breakfast Smoothie to balance the rich sweetness.
• Drizzle with warm chocolate ganache for an extra layer of indulgence.
• Cut into tiny bite-sized squares for a party platter alongside our Peanut butter cheesecake bars.

Storage and Reheating

Do not refrigerate these.

Cold temperatures will turn the marshmallow fluff into a rubbery, unappealing sheet of glue. Instead, store them in an airtight container at room temperature, where they will remain perfectly soft for up to four days.

If you want that fresh-out-of-the-oven experience, a quick zap in the microwave does wonders. Just ten seconds on medium power will soften the peanut butter matrix beautifully.

For long-term storage, you can freeze the sliced bars for up to three months. Wrap each bar tightly in plastic wrap before placing them in a heavy-duty freezer bag to prevent freezer burn. When the craving strikes, let them thaw on the counter for an hour, and they will taste just as good as the day you baked them.

Your patience will be rewarded.

Ingredient Substitutes

If you need to adapt this recipe for dietary needs or pantry limitations, here are the best tested swaps:

1. Peanut Butter: Swap with sunflower seed butter for a nut-free option, but ensure it is a well-emulsified brand.
2. Marshmallow Fluff: You can use mini marshmallows in a pinch, though they will melt differently and create a slightly more pocketed texture.
3. All-Purpose Flour: A 1:1 gluten-free baking flour blend works perfectly here due to the high moisture content of the peanut butter.
4. Brown Sugar: Coconut sugar can be used, though the bars will be slightly drier and less chewy.

These bars are a love letter to childhood kitchen experiments, minus the smoke alarms and ruined pans. Bake a batch, share them with someone who appreciates a good salty-sweet mess, and let me know if they make you as happy as they make me.