Preheat your oven to 325°F (160°C). In a medium bowl, combine graham cracker crumbs and melted butter. Mix until well combined and press the mixture firmly into the bottom of a 9-inch springform pan to form the crust. Bake for 10 minutes, then remove from the oven and let it cool.

In a large mixing bowl, beat the softened cream cheese with an electric mixer until smooth and creamy. Gradually add the powdered sugar and vanilla extract, mixing until well combined.

In a separate bowl, whisk together the banana pudding mix and milk until smooth and thickened. Gently fold the pudding mixture into the cream cheese mixture until fully combined.

In another bowl, whip the heavy cream until stiff peaks form. Carefully fold the whipped cream into the banana cream cheese mixture until no streaks remain.

Pour half of the cheesecake mixture over the cooled crust. Layer half of the sliced bananas on top, followed by half of the crushed vanilla wafers and walnuts, if using. Repeat the layers with the remaining cheesecake mixture, bananas, and crushed wafers.

Cover the cheesecake with plastic wrap and refrigerate for at least 4 hours, or overnight for best results.

Before serving, top with whipped cream and additional crushed vanilla wafers or walnuts if desired.