Mix cornstarch, sugar and salt and add gradually to cold milk in saucepan. Stir constantly over medium heat until mixture is thick and bubbles, 4 to 5 minutes. Beat eggs slightly and add part of hot mixture with a whisk. Blend and return to saucepan. Cook, stirring constantly, for 2 minutes. Remove from heat and blend in butter. Add Vanilla and Banana extract. Cool. Slice 4 bananas and arrange them in your baked pie crust on the bottom. Pour mixture on top of bananas. Chill and then topped with whipped cream or a meringue as desired.