Reese's Peanut Butter Cupcakes

CUPCAKES Preheat oven to 350 degrees. Line muffin tins with paper cupcake liners. Unwrap Reese's Peanut Butter Cups and place one in the bottom of each cupcake. In a seperate bowl, combine cocoa powder, flour, baking powder, and salt. In a mixing bowl, cream butter and sugar. Add eggs one at a time, beating well after each. Beat in vanilla extract. Add dry ingredients, alternating with the sour cream, beginning and ending with the dry ingredients. Divide batter into cupcake liners. Bake for 20 minutes or until a toothpick inserted in the center comes out clean. FROSTING Cream butter and peanut butter together until fluffy. Gradually add sifted powdered sugar, alternating with a little milk at a time. Beat well, until desired consistency. Frost cupcakes.