Place the egg yolks in a small bowl and set aside.
Mix the sugar, cornstarch and salt in a 3 or 4 quart saucepan. Add the milk and cream and cook over medium heat until smooth and thick, stirring constantly with a whisk. Add a couple spoonfuls of the hot milk mixture to the egg yolks, whisking quickly so the liquid does not cook the egg. Whisk in another couple of spoonfuls. Then add the egg mixture to the rest of the warm milk in the pan and cook another 2 to 3 minutes, whisking. Remove from heat and add the butter and vanilla and whisk until smooth.
Pour the filling into a bowl and then cover with plastic wrap, pressing it down on the surface of the custard so a crust doesn't form on top. Let cool to room temperature. Meanwhile, make the pie crust.
CRUST
In a medium bowl, combine the flour and salt. Then cut in the shortening with a pastry blender until pea sized crumbs form.
Add the cold water 1 tablespoon at a time, mixing with a fork between each. You know you have the right amount of water when the dough begins to form a ball that easily holds together.
Wrap the ball in plastic wrap and place in the fridge to chill for 30 minutes.
Roll the chilled dough out in a circle and place in a 9-inch pie plate. Press into the bottom and sides of the pie plate and then flute the edges. Prick the crust with a fork and bake at 375 degrees for about 40 minutes or until lightly golden. Cool completely.
When the filling is cool and the pie crust is cool too, slice 2 bananas and place them in the bottom of the pie shell. Pour the filling on top. Cover the pie with plastic wrap and chill in the fridge for at least 2 hours.
TOPPING
Beat whipping cream and powdered sugar together on high until stiff peaks form.
Top the chilled pie with whipped cream and bananas just before serving.