Banana Cream Pie

9 inch baked pie shell
2/3 cup sugar
1/4 cup corn starch
1/2 tsp salt
3 cups milk
4 egg yolks, slightly beaten
2 Tbs butter
1 tsp vanilla
2 large bananas
Sweetened whipped cream

Bake pie shell. Stir together sugar, cornstarch and salt in saucepan. Blend milk and egg yolks; gradually stir into sugar mixture. Cook over medium heat, stirring contantly, until mixture thickens and boils. Boil and stir one minute. Remove from heat; blend in butter and vanilla. Press plastic wrap onto filling in saucepan and cool to room temperature.
Peel and slice bananas; arrange layer of banana slices 1/2 inch thick. Pour in cooled filling. Chill pie thoroughly, at least 2 hours. Just before serving, top pie with sweetened whipped cream.