4 heaping tbsp. flour
1 c. milk
1/2 c. shortening
1/2 c. butter
1 c. granulated sugar
2 tsp. vanilla

I used 1 cup butter instead.

Mix flour and milk; cook over low heat until thick as paste. Cool. Cream shortening, butter and sugar in mixer for 4 minutes. Add cooled paste and beat 4 minutes more. Blend in vanilla.