01 - Preheat oven to 350°F. Line a 9x9 inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.
02 - Combine crushed vanilla wafers and sugar in a medium bowl. Pour in melted butter and stir until the mixture resembles wet sand. Press firmly and evenly into the bottom of the prepared pan. Bake for 10 minutes, then set aside to cool slightly.
03 - Using an electric mixer, beat softened cream cheese and sugar on medium speed until completely smooth. Add eggs one at a time, beating well after each addition. Blend in vanilla extract, mashed bananas, flour, and sour cream until fully incorporated and no lumps remain.
04 - Pour the cheesecake filling over the baked crust, spreading evenly with a spatula. Bake for 30 minutes, or until the center is set but still has a slight jiggle. Cool at room temperature for 1 hour, then transfer to the refrigerator and chill for at least 2 hours.
05 - In a medium bowl, whisk together the instant banana pudding mix and cold milk for about 2 minutes until smooth and thickened. Spread the pudding evenly over the chilled cheesecake layer. Arrange thinly sliced bananas on top of the pudding in an even layer.
06 - In a chilled bowl, whip the heavy cream, powdered sugar, and vanilla extract until stiff peaks form. Spread the whipped cream evenly over the pudding layer. Garnish with additional banana slices and crushed vanilla wafers if desired.
07 - Refrigerate for at least 1 additional hour to allow all layers to set firmly. Use the parchment overhang to lift the dessert from the pan, then cut into 16 even squares and serve chilled.