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