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A close-up shot of a single square Marshmallow Peanut Butter Brownie on a white plate. The distinct layers of fudgy brownie, swirled peanut butter, and gooey marshmallow are clearly visible.

Marshmallow Peanut Butter Brownies: The Ultimate Gooey Treat

Indulge in the ultimate gooey treat with these Marshmallow Peanut Butter Brownies. A rich, fudgy brownie base is swirled with creamy peanut butter and topped with perfectly toasted marshmallows for a truly decadent and unforgettable dessert experience.
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Prep Time 15 minutes
Cook Time 33 minutes
Total Time 48 minutes
Servings: 16 brownies
Course: Dessert, Snack
Cuisine: American
Calories: 210
Ingredients Equipment Method Notes

Ingredients
  

  • 1/2 cup unsalted butter melted
  • 1 cup granulated sugar
  • 2 large eggs room temperature
  • 1 tsp vanilla extract
  • 1/2 cup all-purpose flour
  • 1/3 cup unsweetened cocoa powder
  • 1/4 tsp baking powder
  • 1/4 tsp salt
  • 1/2 cup creamy peanut butter
  • 2 tbsp powdered sugar
  • 2 cups mini marshmallows

Equipment

  • 1 8x8 inch baking pan
  • 2 Mixing Bowls

Instructions
 

  1. Preheat your oven to 350°F (175°C). Grease and line an 8x8 inch baking pan with parchment paper. In a large bowl, whisk together the melted butter and granulated sugar. Beat in the eggs one at a time, then stir in the vanilla extract.
  2. In a separate bowl, sift the flour, cocoa powder, baking powder, and salt. Add the dry ingredients to the wet ingredients and mix until just combined. Do not overmix.
  3. In a small bowl, mix the creamy peanut butter and powdered sugar until smooth. Pour the brownie batter into the prepared pan. Drop spoonfuls of the peanut butter mixture over the batter, then use a knife to gently swirl it in.
  4. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs.
  5. Remove the brownies from the oven and immediately top with the mini marshmallows. Return to the oven for 2-3 minutes until the marshmallows are puffed. For a toasted top, broil for 30-60 seconds, watching closely.
  6. Let the brownies cool completely in the pan on a wire rack before lifting them out with the parchment paper handles. For best results and clean cuts, chill for at least 1 hour before slicing.

Notes

For Fudgy Brownies: Be careful not to overbake the brownie base before adding the marshmallows. A few moist crumbs on the toothpick is perfect.
Clean Slices: Chilling the brownies is the secret to clean, neat squares. The marshmallow topping can be very sticky when warm.
Storage: Store in an airtight container at room temperature for up to 4 days.
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