Combine graham cracker crumbs and melted butter in a mixing bowl until evenly coated. Press the mixture firmly into the bottom of a cake pan to form an even crust. Bake at 350°F (175°C) for 10 minutes until golden brown, then let it cool.
Place granulated sugar in a saucepan over medium heat. Without stirring initially, allow the sugar to melt and turn a deep amber color, indicating caramelization—watch for bubbling and a rich aroma. Once melted, carefully add heavy cream, stirring constantly until smooth and thickened, about 3-5 minutes. Remove from heat and stir in vanilla extract. Allow caramel to cool slightly.
Spread sliced bananas evenly over the cooled crust. Pour the warm caramel sauce over the bananas, ensuring an even layer. Let it set at room temperature for about 15 minutes to thicken slightly.
Whip the heavy cream with a hand or electric mixer until soft peaks form, approximately 3-4 minutes. Spread the whipped cream over the caramelized banana layer smoothly to cover completely.
Refrigerate the assembled cake for at least 2 hours to set. Just before serving, optionally garnish with additional banana slices or chocolate shavings for presentation.
