Preheat your oven to 350°F (175°C) and prepare two 9-inch round baking pans by greasing them and lining the bottoms with parchment paper.

Sift together the cocoa powder, flour, baking powder, baking soda, and salt in a large mixing bowl.

In another bowl, whisk together the eggs, milk, butter, and vanilla extract until smooth and light in color.

Gradually add the dry ingredients to the wet ingredients, mixing on medium speed until well combined.

Carefully stir in the boiling water until the batter is smooth; the batter will be thin.

Pour the batter evenly into prepared pans and bake for 30-35 minutes, checking for doneness with a toothpick.

Let the cakes cool in the pans for about 10 minutes, then transfer to wire racks to cool completely.

Cream together the softened butter and peanut butter until light and fluffy. Gradually add powdered sugar and heavy cream until desired consistency is reached.

Assemble the cake by layering the first layer on a serving plate, frosting generously, then add the second layer and frost the top and sides.

Decorate with chopped Reese’s cups on top.