1/2 c. butter
1/2 c. solid shortening
1 tsp. vanilla
4 c. (approx. 1 lb.) sifted confectioners' sugar
2 tbsp. milk

In a large mixing bowl, cream butter and shortening with electric mixer. Add vanilla. Gradually add sugar, one cup at a time, beating well on medium speed. Scrape sides and bottom of bowl often. When all the sugar has been mixed in, icing will appear dry. Add milk and beat at high speed until light and fluffy. Keep icing covered with a damp cloth until ready to decorate. Refrigerate when not in use. Keeps for up to 2 weeks in an air tight container. Re-whip before using. Makes 3 cups.