1/2 c. butter
1/4 tsp. salt
5 1/2 c. powdered sugar
1/2 c. shortening
1 1/2 tsp. vanilla
1/4 c. plus 1 tbsp. milk

Cream butter and shortening. Add vanilla and salt. Gradually add sugar, one cup at a time; beat at medium speed. After sugar is added, icing will be dry. Add milk and beat at high speed until light and fluffy. Cover (refrigerate if keeping longer) until ready to use. For regular cake, add more milk - 2 tablespoons.