1/2 c. butter
1/2 c. shortening
1 tsp. flavoring
1/8 tsp. salt
4 c. powdered sugar, sifted
3 tbsp. milk

Cream shortening and butter together. Add vanilla and salt. Beat in sugar 1 cup at a time, blending well after each addition. Add milk and beat at high speed until light and fluffy. Keep covered and store in refrigerator when not in use.