Vanilla Pudding & Filling

1/3 cup all-purpose flour or 3 tablespoons cornstarch
1/4 teaspoon salt
3/4 cup granulated sugar
2 cups whole milk
3 beaten egg yolks
2 tablespoons butter
1 teaspoon vanilla extract

In heavy saucepan whisk together the flour, salt, sugar and milk.  Place over medium heat and cook until bubbly, stirring constantly.  Cook, stirring, for 2 minutes.  Remove from heat and stir some of the mixture into egg yolks, beaten well.  Return this mixture to saucepan, return to heat and cook another 2 minutes, stirring constantly, or until mixture thickens.  Remove from heat; stir in butter and vanilla.  Makes enough to fill a 9-inch pie shell.