Preheat oven to 350.
Line cupcake pan with paper liners.
Prepare batter according to box directions.
Fill liners about 1/2 full with batter.
Place a Reese's into each and gently press in place.
Bake 15-18 minutes.
Allow cupcakes to cool completely.
Cream together the butter and peanut butter.
Slowly adding in the sugar,it gets too thick then adding a little milk to thin.
Continue until all of the sugar is in and the frosting blended and right consistency.
Transfer to piping bag and pipe onto each cupcake.
Chop up remaining peanut butter cups or use chocolate syrup to garnish cupcakes.