1. Prepare Oven and Crust:

• Preheat the oven to 325°F (163°C).
• Line the bottom only of a 9-inch springform pan with a circle of parchment paper. Do not grease the sides (helps cheesecake cling and prevents sinking). Set aside.
• Crush the Nilla wafers into fine crumbs using a food processor, blender, or by placing them in a sealed bag and crushing with a rolling pin.
• In a medium bowl, combine the Nilla wafer crumbs and granulated sugar. Stir well. Add the melted butter and mix until all crumbs are evenly moistened.
• Press the crumb mixture firmly and evenly onto the bottom of the prepared springform pan.
• Bake the crust for 10 minutes. Remove from the oven and set aside on a wire rack to cool slightly while you prepare the filling. Keep the oven on at 325°F (163°C).

2. Prepare for Water Bath:

• While the crust bakes/cools, place a large pot or kettle of water on the stove to boil. You’ll need enough boiling water for the water bath later.
• Wrap the Pan: Tear off large sheets of heavy-duty aluminum foil. Securely wrap the outside bottom and sides of the springform pan with 2 to 3 layers of foil, ensuring there are no gaps or tears where water could seep in.
• Optional Oven Bag: For extra insurance, place the foil-wrapped springform pan inside a large oven bag and roll the sides of the bag down neatly around the pan.

3. Make the Cheesecake Filling:

• Ensure cream cheese is fully softened, and sour cream and eggs are at room temperature.
• In the bowl of a stand mixer fitted with the paddle attachment (or in a large bowl using a handheld mixer), beat the softened cream cheese on low-medium speed until completely smooth and creamy, about 1 to 2 minutes. Scrape down the sides and bottom of the bowl.
• Add the mashed ripe banana and room temperature sour cream. Mix on low-medium speed until fully combined, scraping the bowl as needed.
• Add the granulated sugar, the dry instant banana cream pudding mix, and the pure vanilla extract. Mix on low speed until well combined, about 30 to 60 seconds. Scrape the bowl again.
• In a separate small bowl, lightly beat the room temperature eggs with a fork.
• With the mixer on low speed, slowly pour the beaten eggs into the cheesecake filling. Mix only until just combined. Do not overmix once the eggs are added, as this can incorporate too much air and lead to cracks.
• Remove the bowl from the mixer. Use a rubber spatula to give the filling a few final folds, ensuring everything from the bottom is incorporated.

4. Assemble and Prepare for Baking:

• Pour the cheesecake filling over the slightly cooled Nilla wafer crust in the springform pan. Smooth the top into an even layer.
• Place the large roasting pan (that will hold the water bath) in the preheated oven. Carefully place the wrapped springform pan inside the roasting pan.
• Very carefully pour the boiling water you prepared earlier into the roasting pan around the springform pan, until the water reaches about 1-inch deep up the sides of the springform pan. Be careful not to splash water onto the cheesecake batter.

5. Bake the Cheesecake:

• Carefully slide the oven rack with the roasting pan back into the oven.
• Bake for 70 to 80 minutes. The cheesecake is done when the edges are set and slightly puffed, but the center still has a slight jiggle when you gently nudge the pan.

6. Cool Gradually:

• Turn the oven off completely. Crack the oven door open slightly (prop it with a wooden spoon if needed).
• Allow the cheesecake to cool slowly in the warm, turned-off oven for 1 hour. This gradual cooling process is crucial for preventing cracks.

7. Cool Completely and Chill:

• After 1 hour in the cooling oven, carefully remove the roasting pan from the oven. Lift the springform pan out of the water bath and remove the oven bag (if used) and the aluminum foil wrapping.
• Place the cheesecake (still in the springform pan) on a wire rack and let it cool completely to room temperature.
• Once completely cool, cover the cheesecake tightly with plastic wrap (or foil) and transfer it to the refrigerator.
• Chill for at least 5 to 6 hours, or preferably overnight, until completely cold and firm. Thorough chilling is essential for the best texture and flavor.

8. Decorate and Serve:

• Once the cheesecake is completely cooled and thoroughly chilled, run a thin, flexible knife or offset spatula around the outside edge of the cheesecake to loosen it from the pan sides.
• Carefully release and remove the springform pan ring.
• Decorate the top of the cheesecake just before serving. Spread or pipe a generous amount of whipped cream (homemade or store-bought) over the top. Arrange fresh banana slices and whole Nilla wafers decoratively on the whipped cream.
• Slice with a large, sharp knife dipped in hot water and wiped clean between cuts for neatest slices. Serve chilled.