- 1 box Brownie Mix
- 1/4 cup Water
- 1/2 cup Oil
- 1 Egg
- 4 tablespoons Unsalted Butter, Melted
- 1/2 cup Powdered Sugar
- 1 cup Creamy Peanut Butter
- 1 teaspoon Pure Vanilla Extract
- 1 cup Reese's Pieces, Divided
Preheat oven to 325°F.
In a large bowl, combine brownie mix, water, oil, and egg.
Spread half of the brownie batter into a greased 8x8-inch pan.
In a medium bowl, combine butter, powdered sugar, peanut butter, and vanilla, stirring until smooth.
Drop half of the peanut butter filling by tablespoonful onto the brownie batter in the pan. Using a knife, lightly swirl the peanut butter filling.
Sprinkle with half of the Reese's pieces.
Spread the remaining brownie batter into the pan.
Drop the remaining peanut butter filling by tablespoonful onto the brownie batter. Using a knife, lightly swirl it.
Sprinkle with remaining Reese's pieces.
Bake for 50-55 minutes, or until a knife inserted near the center comes out clean.
Remove to a wire rack to cool completely.
Cut into bars, and enjoy!
- The peanut butter filling thickens very quickly as the melted butter sets. If it’s too thick to drop by spoonful and easily swirl, you can pop it in the microwave for 5-10 seconds to thin it out.