Mix sugar, cornstarch, and salt in saucepan.
Slowly stir in milk. Cook over medium, stirring constantly, until mixture thickens and boils. Boil for 1-2 minutes. Reduce heat to low for the next two steps.
Beat eggs, slightly in a glass measuring bowl.
Pour 1 c. of the hot milk liquid from the saucepan over the eggs and stir with a fork.
Pour the egg and milk mixture BACK INTO THE PAN. Boil and stir for 1-2 minutes, remove from heat.
Stir in butter and vanilla.
Press a piece of plastic wrap onto the custard and allow to cool until room temperature in the refrigerator.
While the custard cools, make the pie crust.
Mix flour and salt together. Cut in butter and shortening with a pastry cutter. Stir in oil.
Combine milk and lemon juice (or vinegar) together and stir into pie crust until the dough comes together. Knead over a lightly floured surface until smooth.
Roll out to fit a 9-inch pie pan.
Poke holes across the bottom, using a fork, and crimp edges. Bake at 450 degrees for 8-10 minutes, or until edges are lightly golden. Cool.
Slice two of the bananas.
Place them into the cooled pie crust in a single layer.
Top with cooled custard.
Beat whipping cream and powdered sugar with an electric mixer until stiff peaks form. Top pie with homemade whipping cream.
Refrigerate until ready to serve, AT LEAST 1 hour. Add extra banana slices as a garnish, just before serving.