Buttercream Frosting
["1/2 c. margarine", "1/2 c. shortening", "1 c. sugar", "3/4 c. lukewarm milk", "1 tsp. vanilla"]
["Cream margarine and shortening. Beat in sugar and milk alternately. Beat vigorously until granules cannot be felt between fingers (on high speed with electric beater for 10 minutes). Blend in vanilla."]
["margarine", "shortening", "sugar", "milk", "vanilla"]