Crust: Preheat your oven to 325°F (160°C). In a bowl, mix the vanilla wafer crumbs, melted butter, and sugar together. Press this mix into the bottom of a springform pan firmly. Bake for 10 minutes, then set aside to cool.

Cheesecake Filling: Lower the oven temperature to 300°F (150°C). In another bowl, combine the cream cheese, 1 cup of sugar, flour, sour cream, and banana extract until smooth. Add the pureed bananas and eggs, mixing well. Pour this mixture over your baked crust, and bake in a water bath for 1 hour and 30 minutes.

Bavarian Cream: While the cheesecake cools, sprinkle the gelatin over the milk and let it sit for a few minutes. Whisk the egg yolks in a separate bowl. In a saucepan, heat the heavy cream and sugar until warm, then gradually add a bit of this mixture to the yolks while whisking. Cook until thickened, then stir in the gelatin until dissolved. Let cool, then whip the 2/3 cup heavy cream with 5 tablespoons of powdered sugar and fold it into the custard. Spread this Bavarian cream over your cooled cheesecake.

Topping: Whip the remaining heavy cream, sugar, and vanilla until soft peaks form. Decorate your cheesecake with this whipped cream and place fresh sliced bananas on top.