I use the recipe on the container of Hershey's Cocoa, natural unsweetened. It's called "Perfectly Chocolate" Chocolate Frosting.
1 stick (1/2 c) butter or margarine 3 c powdered sugar 1 tsp. vanilla extract
2/3 c Hershey's Cocoa 1/3 c milk
Melt butter. Stir in cocoa. Alternately add powdered sugar and milk, beating on med. speed to spreading consistency. Add more milk, if needed. Stir in vanilla. Makes about 2 cups.
This is very good. I just use a cake mix for the cake and top with this delicious frosting. Taste like homemade!