1 cup butter, softened
1 cup white sugar
4 tablespoons all-purpose flour
1 cup milk
1 teaspoon vanilla extract
In small saucepan cook flour and milk until thick, stirring constantly.
Cool to room temperature.
With an electric mixer, beat butter and sugar until fluffy. (like 15 minutes!!)
Beat both mixtures together on high speed until fluffy and smooth.
Add vanilla and beat until combined.
Refrigerate for about 1/2 hour, until it is of spreading consistency.