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