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 granulated sugar in a medium bowl. Pour in melted butter and stir until the mixture resembles wet sand. Press the crumb mixture 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 the softened cream cheese and sugar in a large bowl on medium speed until completely smooth. Add the eggs one at a time, beating well after each addition. Blend in the vanilla extract, mashed bananas, flour, and sour cream until the batter is fully incorporated and creamy.
04 - Pour the cheesecake filling over the cooled crust, spreading it into an even layer 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 - Whisk the instant banana pudding mix and cold whole milk together in a medium bowl for about 2 minutes until smooth and thickened. Spread the pudding evenly over the chilled cheesecake layer. Arrange thin banana slices across the surface of the pudding.
06 - In a chilled bowl, whip the heavy cream, powdered sugar, and vanilla extract with an electric mixer until stiff peaks form. Spread the whipped cream evenly over the pudding layer. Garnish with additional banana slices and crushed vanilla wafers if desired. Refrigerate for at least 1 more hour before cutting into 16 squares and serving.