Combine the milk, vanilla beans and vanilla pod or vanilla bean paste in a heavy saucepan, and heat over medium heat until barely steaming.

In a medium-size bowl, whisk together the yolks, cornstarch, flour and sugar.

Gradually temper the warm milk into the egg mixture while whisking.

Pour the custard back into the saucepan and cook over medium-low heat, whisking frequently, until the custard has thickened. Remove the vanilla pod.

Transfer the custard to a bowl and whisk in the butter and rum. Cover the custard with plastic wrap directly touching the surface of the custard, and allow to chill until cold, about 2 hours.

In a large bowl, measure together the heavy cream and powdered sugar. Using a large whisk or an electric mixer, whip the cream to medium peaks.

To assemble the pie, layer the banana slices on the bottom of the Blind Baked Crust. Evenly top with the chilled custard. Dollop the whipped cream on top, and serve.