Prepare the crust: Preheat your oven to 325°F (163°C). Mix the vanilla wafer crumbs, melted butter, and sugar in a bowl until well combined. Press the mixture into the bottom and up the sides of a 9-inch (23cm) springform pan. Bake for 10 minutes, then set aside to cool.

Make the cheesecake filling: In a large bowl, beat the cream cheese, sugar, and flour together until smooth. Add the sour cream and banana extract and mix until well combined. Add the pureed banana and mix until smooth. Beat in the eggs one at a time on low speed, scraping down the sides as necessary.

Bake the cheesecake: Pour the filling into the prepared crust. Place the springform pan in a larger pan and fill the outside pan with warm water halfway up the side of the cheesecake pan (this creates a water bath). Bake for 1 hour 30 minutes, or until the center is set but still jiggly. Turn off the oven and let the cheesecake cool in the oven for 30 minutes with the door slightly cracked. Remove from the oven and cool to room temperature before refrigerating for at least 4 hours or overnight.

Prepare the Bavarian cream topping: In a small bowl, sprinkle the gelatin over the milk and set aside. In a medium bowl, whisk the egg yolks. In a saucepan, heat 1/2 cup heavy cream, sugar, vanilla, and banana extract until warm. Slowly pour the cream into the egg yolks to temper them. Return the mixture to the saucepan and cook until thickened. Add the gelatin mixture and stir until smooth. Set the custard bowl in a larger bowl of ice and stir occasionally to cool.

Whip the cream: Once the custard has cooled to room temperature, whip 2/3 cup of cold heavy whipping cream with powdered sugar until stiff peaks form. Gently fold the whipped cream into the custard until smooth. Spread the Bavarian cream over the chilled cheesecake.

Top and serve: Once the cheesecake has set in the fridge, remove it from the springform pan. Top with fresh banana slices and whipped cream. Slice and serve!