Mom`s Old Fashioned Butterscotch Pie

1 cup packed light brown sugar 4 tablespoons cornstarch 1/2 teaspoon salt 2 cups milk
2 egg yolks, beaten 1 tablespoon butter 1 teaspoon vanilla extract 1 (9 inch) pie crust, baked

In top of double boiler, combine brown sugar, cornstarch, salt and milk. Stir and keep stirring until it thickens.
Mix in egg yolks, stir and keep cooking until it thickens.
Remove from heat, and add butter or margarine and vanilla. Keep stirring.
Pour into cooked pie crust. Bake at 400 degrees for 5 minutes or until brown.

If you don't have a double boiler, don't worry. It will still work just fine just use medium heat and stir constantly .Tastes great with whipped cream on top.