Sandwiching a Reese's peanut butter cup between a fudgy, chewy brownie may be one of the world's most decadent desserts ever created to elevate a boxed brownie mix.
Preheat oven to 350 °F (177 °C) and grease a 9x9 baking pan with cooking spray and line with parchment paper. Set aside.
Mix together brownie mix with ingredients according to the box to form the brownie batter.
18 ounce box of your favorite brownie mix
Pour half the batter into the prepared baking pan and spread into an even layer with a spatula.
Place Reese's cups on top of the brownie batter. There should be 4 in each row.
16 Reese's peanut butter cups
Pour the rest of the brownie batter on top of the Reese's cups, covering them. Spread the batter gently with a spatula to make sure everything is covered.
Bake for 35-40 minutes then remove from oven and let brownies cool in pan until room temperature.
Using a paring knife, run it around the edge of the pan to loosen the brownies. Slice into squares, you should get 16 so each brownie square has a Reese's peanut butter cup in the center.
Store in airtight container for up to 4 days at room temperature.