These Fluffernutter Bars are the ultimate nostalgic treat, bringing together the classic duo of creamy peanut butter and sweet marshmallow fluff in a decadent, shareable dessert. Featuring a dense, chewy peanut butter blondie base and a cloud-like marshmallow frosting, these bars are a guaranteed crowd-pleaser for bake sales, potlucks, or family movie nights.
Every bite offers a perfect harmony of salty and sweet, finished with a generous sprinkle of chopped peanuts for an extra layer of crunch.
Recipe Details
- Flavor Profile: A rich, nutty peanut butter base complemented by a sugary, airy marshmallow topping and savory roasted peanuts.
- Textures: The bottom layer is soft and chewy, while the frosting is light and silky, topped with a satisfyingly crisp nutty finish.
- Time: Approximately 15 minutes of prep time and 25 to 30 minutes of baking, plus time for cooling.
- Difficulty: Easy. This recipe uses standard mixing methods and simple assembly that any home baker can achieve.
What You’ll Need
This recipe is divided into two parts: a sturdy peanut butter base and a fluffy frosting. You will need pantry staples like flour, sugars, and butter, along with creamy peanut butter and a container of marshmallow fluff to create the signature “fluffernutter” experience.
Ingredient Notes
- Creamy Peanut Butter – This provides the core flavor and moisture for the bars. A standard creamy variety works best for a consistent, smooth texture.
- Marshmallow Fluff – The star of the frosting, this gives the topping its unique, light-as-air consistency that standard marshmallows cannot replicate.
- Unsalted Butter – Melted butter is used in the base for chewiness, while softened butter is essential in the frosting for a stable, creamy structure.
- Brown Sugar – This adds a hint of molasses flavor and ensures the bars stay moist and soft.
- Chopped Peanuts – These are sprinkled on top to provide a salty contrast to the sweet marshmallow layer.
Add-ins and Substitutions
- Chocolate Drizzle – For a “Reese’s” twist, you can drizzle melted semi-sweet chocolate over the finished frosting and peanuts.
- Peanut Butter Chips – For even more peanut flavor, fold 1/2 cup of peanut butter chips into the batter before baking.
- Sea Salt – A tiny pinch of flaked sea salt over the frosting can further enhance the sweet and salty dynamic.
How to Make Fluffernutter Bars
This recipe requires the bars to be completely cool before frosting to ensure the marshmallow topping stays perfectly fluffy.
- Preheat and Prep: Begin by preheating your oven to 350 degrees. Grease a 9×13 inch baking pan with nonstick cooking spray and set it aside.
- Mix the Wet Ingredients: In a large bowl, use a hand mixer to blend the 3/4 cup melted butter with the brown sugar and granulated sugar. Once blended, add the eggs and vanilla extract, beating until fully incorporated.
- Add Peanut Butter: Add the 3/4 cup creamy peanut butter to the mixture and continue to beat until the batter is smooth and combined.
- Incorporate Dry Ingredients: In a separate bowl, whisk together the salt and all-purpose flour. Slowly add this to your wet mixture, mixing until just combined. Be careful not to overwork the dough.
- Bake: Spread the batter evenly into the prepared 9×13 pan. Bake for 25 to 30 minutes until the edges are golden and a toothpick inserted into the center comes out clean.
- Cooling: Remove the bars from the oven and let them cool completely in the pan. This is vital, as frosting a warm bar will cause the marshmallow fluff to melt.
- Make the Frosting: In a large bowl, beat together the softened butter and the 7-ounce container of marshmallow fluff until smooth.
- Add Sugar: Gradually add the powdered sugar, 1 cup at a time, beating after each addition until the frosting is blended and fluffy.
- Final Assembly: Spread the frosting evenly over the cooled bars and sprinkle the 1/2 cup of chopped peanuts over the top.
Pro Tip: For the fluffiest frosting, make sure your butter is truly softened to room temperature but not melty. This allows the marshmallow fluff to emulsify properly for a stable topping.
Recipe Tips
- Cooling is Crucial: Do not attempt to frost these bars while they are even slightly warm. The marshmallow-based frosting is delicate and needs a stone-cold base to sit on.
- Don’t Overmix: When adding the flour, mix only until no white streaks remain. Overmixing can lead to a tough, bready bar rather than a chewy one.
- Clean Slicing: To get perfectly clean squares, chill the frosted bars in the refrigerator for 20 minutes before cutting with a sharp, warm knife.
- Even Spreading: Use an offset spatula to spread the peanut butter batter into the corners of the 9×13 pan for even baking.
FAQs
Can I use crunchy peanut butter? While creamy is recommended for the best texture in the base, you can use crunchy if you prefer extra bits of peanuts throughout the bar itself.
What if I don’t have marshmallow fluff? Marshmallow fluff is specifically designed for frostings like this. Using melted marshmallows will result in a much stickier, chewier texture that is harder to spread and cut.
How should I store these? Store the bars in an airtight container. Because of the frosting, they are best kept in a single layer to prevent sticking. They stay fresh at room temperature for up to three days.
Serving Suggestions
- Cold Milk – Nothing beats the combination of peanut butter and a cold glass of milk.
- Coffee – The salty-sweet profile makes these an excellent companion to a bitter dark roast coffee.
- Ice Cream – Serve a square alongside a scoop of chocolate ice cream for a decadent dessert plate.
Make This Recipe in Advance
You can bake the peanut butter base a day in advance. Simply cover the cooled pan tightly with foil and store at room temperature. The frosting is best made and applied on the day you plan to serve, though once frosted, the bars hold up well for several days in a cool environment.
Classic Fluffernutter Blondie Bars with Marshmallow Frosting
- Total Time: 45 minutes
- Yield: 24 Bars 1x
- Diet: Vegetarian
Description
The ultimate nostalgic treat, bringing together creamy peanut butter and sweet marshmallow fluff. Featuring a dense, chewy peanut butter blondie base and a cloud-like marshmallow frosting, these bars offer a perfect harmony of salty and sweet, finished with crunchy roasted peanuts.
Ingredients
The Peanut Butter Base
- 3/4 cup unsalted butter, melted
- 3/4 cup creamy peanut butter
- 1 1/2 cups all-purpose flour
- 1 cup brown sugar & 1/2 cup granulated sugar
- 2 large eggs, 2 tsp vanilla, 1/2 tsp salt
The Marshmallow Frosting
- 1 (7-oz) container marshmallow fluff
- 2 cups powdered sugar
- 1/2 cup unsalted butter, softened
- Topping: 1/2 cup chopped roasted peanuts
Instructions
Prep: Preheat oven to 350°F. Grease a 9×13-inch pan.
Mix: Beat melted butter with sugars. Add eggs, vanilla, and peanut butter; mix until smooth. Gently stir in flour and salt.
Bake: Spread into pan. Bake for 25–30 mins until golden. Cool completely.
Frosting: Beat softened butter and fluff until smooth. Gradually add powdered sugar until light and fluffy.
Assemble: Spread frosting over cooled bars and sprinkle with chopped peanuts. Chill before slicing.
Notes
The ‘Meltdown’ Warning: Marshmallow fluff is temperature-sensitive; the base must be cold to the touch to prevent the frosting from turning into a glaze.
Softened vs. Melted: Use room temperature butter for the frosting to hold the air bubbles needed for stability.
Texture Control: Stop mixing the blondie base as soon as flour streaks disappear to keep the bars fudgy rather than bread-like.
- Prep Time: 15 minutes
- Cook Time: 30 minutes
- Category: Dessert / Snack
- Method: Beating / Baking
- Cuisine: American Nostalgia
Nutrition
- Serving Size: 1 Bar
- Calories: 280
- Sugar: 26
- Sodium: 145
- Fat: 16
- Saturated Fat: 8
- Unsaturated Fat: 8
- Trans Fat: 0.3
- Carbohydrates: 32
- Fiber: 1
- Protein: 4
- Cholesterol: 40
Keywords: fluffernutter bars, peanut butter marshmallow bars, marshmallow fluff frosting, peanut butter blondies, sweet and salty desserts, easy bake sale recipes, childhood nostalgia treats
