Mormor's Magic Mix aka Peanut Butter Frosting
1 C smooth Peanut Butter
1 lb. C&H powdered sugar
1/2 C milk
Mix the peanut butter and powdered sugar together and slowly add milk until you reach a spreadable consistency.
Put into a pastry bag with a #27 tip and swirl onto the tops of the brownies.
Other suggestions are vanilla frosting with sprinkles or even cream cheese frosting.