Cooked Icing

I have tried this recipe and it is goood. This recipe comes from 1967

Cooked Icing

7 Tablespoon flour
1 cup milk
1 cup sugar
2 sticks butter
2 Tablespoons milk
1 teaspoon vanilla

Cook flour and 1 cup milk in top of double boiler until consistency of mashed potatoes. Cover and cool. Combine sugar, butter ,2 Tablespoon milk and vanilla, then flour mixture. Beat for 15 minutes and frost warm cake.