In the bowl of a stand mixer, combine the brownie mix, egg, cream cheese and butter until it is well mixed.
Spread the batter in a greased 8x8 pan.
Take the frozen Reese's peanut butter cups and press them into the brownie batter in a 4x4 grid pattern. They should be pressed in enough that the top of the Reese's cup is at the same height as the brownie batter.
Bake the brownies at 350 degrees for about 28 minutes.
While the brownies are baking, make the peanut butter frosting. Using a stand mixer, blend together peanut butter, powdered sugar, butter, and milk 2-3 minutes or until light and fluffy.
Once the brownies are cool, spread the frosting on top of the brownies.
Place 2 ounces of chocolate in a microwave safe bowl. Heat the chocolate in 15 second intervals, stirring in between until the chocolate is completely melted. Do this slowly so the chocolate doesn't burn.
Drizzle the melted chocolate on top of the peanut butter frosting and allow the brownies to set.
Store in an airtight container.
Make 1/2 a recipe of peanut butter frosting if you want a thinner frosting layer.The calories shown are based on the cake being cut into 16 pieces and all of the frosting used, with 1 serving being 1 frosted brownie. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.