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

Mix flour and milk in saucepan. Cook over low heat until thick. Put in saucer to cool. Cream butter and shortening with electric mixer 4 minutes. Add sugar gradually while mixing and beat another 4 minutes. Add cooled flour paste and beat another 4 minutes. Add vanilla and blend in well. The trick is in the mixing.