Email to Sue Arnold Peanut Butter Frosting Source of Recipe Jif Peanut Butter Cookbook List of Ingredients 1/4 C. butter or margarine 2 C. powdered sugar 3 Tbsp. milk 1 tsp. vanilla 1/2 C. creamy peanut butter Instructions Melt butter. Beat in powdered sugar, milk and vanilla. Blend in peanut butter. Frosts one 13x9 inch cake.