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Stack of 3 gooey fluffernutter bars.

Fluffernutter Bars

Soft and chewy peanut butter bars with a layer of gooey marshmallow in the middle. If you love the classic sandwich or the combo of sweet and salty - then these fluffernutter bars are for you.
Course Dessert
Cuisine American
Keyword Fluffernutter Bars
Prep Time 30 minutes
Cook Time 35 minutes
Total Time 1 hour 5 minutes
Servings 15 bars
Calories 410kcal


  • 9x13 Inch Pan


  • 2 ¼ cups all-purpose flour
  • 1 teaspoon baking powder
  • ¼ teaspoon salt
  • ¾ cup unsalted butter softened
  • ¾ cup brown sugar
  • cup white sugar
  • 1 ½ 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


  • Preheat the oven to 350F degrees and place the oven rack in the middle of the oven.
  • Line a 9x13 inch pan* with parchment paper, leaving an overhang around the edges. Or line with aluminum foil and lightly grease.
  • In a medium bowl whisk together the flour, baking powder and salt.
  • In a separate large bowl beat together the butter, brown sugar and white sugar until soft.
  • Beat in the peanut butter. Then mix in the egg and egg yolk until smooth.
  • With the mixer on low speed, mix the flour mixture into the peanut butter mixture about ½ at a time.
  • Remove about 1 cup of batter from the bowl.
  • Press the rest of the peanut butter dough into the bottom of the lined pan, to form an even layer.
  • Bake the peanut butter layer in the preheated oven for 25 minutes, or until the top looks fully set.
  • Remove the pan from the oven (keep the oven turned on). Carefully spread the entire jar of marshmallow fluff on top of the peanut butter layer.
  • Pinch of pieces of the reserved peanut butter cookie dough, flatten them slightly into pieces about 1 inch in size and place on top of the marshmallow layer. You do not need to entirely cover the marshmallow layer - mine was about 80-90% covered.
  • Place the pan back in the oven and bake for 10 minutes, or until the peanut butter layer on top is set.
  • Remove the pan from the oven and let the bars cool at room temperature for at least 1 hour before slicing.
  • Before slicing, lift the bars out of the pan using the overhang of the parchment paper/aluminum foil and place on a cutting board.
  • Slightly grease a thin, sharp knife with non-stick cooking spray (this is optional - but helps to avoid the marshmallow layer sticking onto the knife) and slice the bars.


  1. I do not recommend using natural or homemade peanut butter (or any peanut butter without stabilizers) because it can separate and lead to too much oil or not enough oil. If using crunchy peanut butter - use 1 ¾ cups instead.
  2. Using a metal pan will make the edges crispier, whereas a glass pan will make the edges a little less crispy. 
  3. Store bars in an airtight container at room temperature for up to 5 days.
  4. Nutrition information is based on 1 bar, assuming the recipe is sliced into 15 even-sized pieces. It is meant as an estimate only. 


Calories: 410kcal | Carbohydrates: 46g | Protein: 9g | Fat: 23g | Saturated Fat: 9g | Cholesterol: 49mg | Sodium: 167mg | Potassium: 236mg | Fiber: 2g | Sugar: 26g | Vitamin A: 318IU | Calcium: 41mg | Iron: 2mg