Step 1: Prepare the Graham Cracker Crust

1. Preheat your oven to 325°F (165°C). Line the bottom of a 9-inch springform pan with parchment paper and lightly grease the sides.
2. In a medium bowl, combine the graham cracker crumbs, melted butter, and sugar. Mix until the crumbs are evenly coated and the mixture resembles wet sand.
3. Press the mixture firmly into the bottom of the prepared springform pan using the back of a spoon or a flat-bottomed glass.
4. Bake the crust for 10 minutes, then remove it from the oven and allow it to cool while you prepare the filling.

Step 2: Make the Banana Cheesecake Filling

1. In a large mixing bowl, beat the softened cream cheese and granulated sugar with an electric mixer on medium speed until smooth and creamy.
2. Add the eggs, one at a time, mixing well after each addition. Be careful not to overmix, as this can add too much air and cause cracks.
3. Stir in the mashed bananas, sour cream, vanilla extract, and flour until just combined. Scrape down the sides of the bowl to ensure the filling is evenly mixed.
4. Pour the cheesecake filling over the cooled crust, spreading it evenly with a spatula.

Step 3: Bake the Cheesecake

1. To prevent cracks, prepare a water bath by wrapping the bottom of the springform pan with aluminum foil to make it watertight. Place the pan into a larger roasting pan and fill the roasting pan with hot water until it reaches about halfway up the sides of the springform pan.
2. Bake the cheesecake in the preheated oven for 60–70 minutes, or until the edges are set and the center is slightly jiggly.
3. Turn off the oven, crack the oven door open, and let the cheesecake cool inside for 1 hour. This gradual cooling prevents cracks.
4. Remove the cheesecake from the water bath and allow it to cool completely at room temperature. Then, refrigerate for at least 4–6 hours or overnight to set.

Step 4: Make the Caramel Sauce

1. In a saucepan over medium heat, combine the sugar and water. Stir gently until the sugar dissolves.
2. Let the mixture boil without stirring until it turns an amber color. Be sure to keep a close eye on it, as caramel can burn quickly.
3. Carefully pour in the heavy cream while stirring. The mixture will bubble up, so be cautious. Stir until smooth.
4. Remove the saucepan from the heat and stir in the butter and sea salt (if using). Allow the caramel sauce to cool slightly before using.

Step 5: Assemble and Garnish the Cheesecake

1. Before serving, top the chilled cheesecake with banana slices arranged in a decorative pattern.
2. Drizzle generously with the caramel sauce and sprinkle with chopped toasted nuts.
3. Add dollops of whipped cream, if desired, and serve with extra caramel sauce on the side for dipping.