Prepare the Crust:

1. Preheat the oven to 325°F (165°C).
2. In a bowl, combine the graham cracker crumbs, sugar, and melted butter. Mix until evenly moistened.
3. Press the mixture firmly into the bottom of a 9-inch springform pan. Bake for 8-10 minutes, then set aside to cool.

Make the Filling:

1. In a large mixing bowl, beat the cream cheese and sugar until smooth and creamy.
2. Add the eggs one at a time, mixing well after each addition.
3. Stir in the vanilla extract and mashed bananas. Mix until fully combined.
4. Fold in the heavy cream gently until the mixture is smooth.

Bake the Cheesecake:

1. Pour the filling over the cooled crust, spreading it evenly.
2. Bake in the preheated oven for 50-60 minutes, or until the center is set but slightly jiggly.
3. Turn off the oven, crack the door slightly, and let the cheesecake cool inside for 1 hour.

Chill and Add Topping:

1. Transfer the cheesecake to the refrigerator and chill for at least 4 hours, or overnight.
2. Before serving, whip the heavy cream, powdered sugar, and vanilla extract until stiff peaks form. Spread or pipe the whipped cream on top of the cheesecake.
3. Garnish with fresh banana slices if desired.