01 - Preheat oven to 340°F. Line the base of a 9-inch springform pan with parchment paper and lightly grease the sides.
02 - Combine crushed graham crackers, sugar, and melted butter in a mixing bowl until evenly moistened. Press the mixture firmly into the bottom of the prepared pan to form an even layer. Bake for 10 minutes, then set aside to cool completely.
03 - Using an electric mixer, beat softened cream cheese and sugar on medium speed until smooth and free of lumps. Add eggs one at a time, beating well after each addition. Blend in mashed bananas, vanilla extract, sour cream, and cornstarch until the mixture is fully incorporated and creamy.
04 - Pour the filling over the cooled crust and smooth the surface with a spatula. Bake for 50 to 60 minutes, until the edges are set and the center retains a slight wobble when gently shaken.
05 - Allow the cheesecake to cool at room temperature for 1 hour. Transfer to the refrigerator and chill for at least 3 hours, or preferably overnight, until fully set.
06 - Toss sliced strawberries with strawberry preserves and fresh lemon juice in a bowl until evenly coated. Arrange the strawberry mixture over the top of the chilled cheesecake.
07 - Decorate with additional fresh banana and strawberry slices if desired. Slice into portions and serve chilled.