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 mixing 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 - Beat cream cheese and sugar together in a large bowl 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, smoothing the top with a spatula. Bake for 30 minutes, or until the center is set but still slightly wobbly. Cool at room temperature for 1 hour, then refrigerate for at least 2 hours.
05 - Whisk together the instant banana pudding mix and cold milk in a medium bowl until smooth and thickened, about 2 minutes. Spread the pudding evenly over the chilled cheesecake layer. Arrange thinly sliced banana on top of the pudding.
06 - Beat heavy whipping cream, powdered sugar, and vanilla extract with an electric mixer until stiff peaks form. Spread the whipped cream evenly over the pudding layer.
07 - Garnish with additional banana slices and crushed vanilla wafers if desired. Chill for at least 1 more hour before cutting into 16 squares and serving.