1/2 c. butter
1/2 c. soft shortening (Crisco)
1 c. granulated sugar
3 tbsp. flour
2/3 c. milk
1 tsp. vanilla

At high speed, beat the butter and shortening until creamy. Add sugar and flour gradually, beating all the while so you have a smooth, creamy mixture. Turn the speed down, so the milk won't splatter, then gradually mix in milk and flavoring. Turn speed up and beat about 5 minutes or until smooth and creamy.