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

Combine flour and milk in a small sauce pan. Cook over medium heat until boils and makes a very thick paste. Remove from heat and chill. Beat together butter and shortening in mixing bowl. While beating on high speed, add sugar by tablespoonfuls until no longer grainy. Beat in vanilla. Continue beating and drop by tablespoonfuls of milk mixture in until filling is light and fluffy. Great in or on chocolate cake.