In a saucepan, combine sugar, cornstarch and salt. Mix well. Gradually stir in milk.
Cook over medium heat, stirring constantly until the mixture thickens and boils. Boil 1 minute. Remove from heat.
Place egg yolks in a medium mixing bowl and gradually stir in at least half of the hot milk mixture. Then blend the egg yolk mixture back into the saucepan. Boil 1 minute more, stirring constantly. Remove from heat.
Blend in butter and vanilla. Cool, stirring occasionally.
Pour into baked pie shell and chill thoroughly, at least 2 hours.
Top with stabilized, sweetened whipped cream.
Variations:
Almond Cream Pie: Follow key recipe above, except in place of vanilla, use 1/2 teaspoon almond extract and add 1/2 cup toasted, slivered blanched almonds to the cooled filling. Sprinkle a few toasted, slivered almonds over the whipped cream topping.
Banana Cream Pie: You will need 3 large bananas. Slice the bananas and arrange in the bottom of the pastry shell before pouring in the cooled filling. Top with whipped cream and toasted, sliced almonds.
Chocolate Cream Pie: Increase sugar to 1 1/2 cups. Choose and add either three one-ounce squares unsweetened chocolate or 1/2 cup cocoa. Unsweetened chocolate is added with the milk. The cocoa is added with the sugar, cornstarch and salt.
Coconut Cream Pie: Fold in 3/4 cup moist shredded coconut just before filling baked pie shell. Sprinkle top of whipped cream with 1/4 cup toasted, shredded coconut.