Source: older Fannie Farmer cookbook
In a small saucepan, cook until thick:
1 cup milk 4 tablespoons all-purpose flour
Set aside until cool.
Combine:
1/2 cup (1 stick) butter 1/2 cup shortening 1 cup granulated sugar
Beat for 4 minutes.
Add milk mixture. Beat 3 minutes. Add 1 teaspoon vanilla extract. Beat 2 minutes.
