Buttery Decorator Icing

½ cup butter or margarine, softened
¼ cup shortening
1 teaspoon vanilla
1/8 teaspoon salt
4 cups powdered sugar
2 to 4 tablespoons milk

In large bowl, beat butter and shortening until light and fluffy. Add vanilla and salt. Beat in powdered sugar 1 cup at a time, scraping down sides of bowl. Add 2 tablespoons milk; beat at high speed until light and fluffy. Add enough additional milk for desired spreading consistency. 3 cups.