Combine egg yolks, sugar, salt, cornstarch, flour and milk. Cook over medium heat stirring until it thickens and boils. Boil 2 minutes. Remove from heat. Blend in butter and vanilla. Pour into baked pie shell or graham cracker crust.
Meringue: Beat until frothy 3 egg whites, 1/4 tsp cream of tartar. Gradually beat in 6 tbl sugar. Continue beating until stiff and glossy. Spread over top of pie and bake 400° F for 8 to 10 minutes.
Banana Cream Pie: Add 3 sliced bananas.
Almond Cream Pie: Add 1/2 tsp almond extract in place of vanilla and add 1/2 cup almonds.
Chocolate Cream Pie: Increase sugar to 1 1/2cups. Add 7 tbl cocoa with the milk.
Coconut Cream Pie: Fold in 3/4 cup flaked coconut. Sprinkle meringue with 1/4 cup coconut.