01 - Preheat the oven to 340°F. Line a 9-inch springform pan with parchment paper on the base and lightly grease the sides.
02 - In a mixing bowl, combine the crushed graham crackers, sugar, and melted butter until evenly moistened. Press the mixture firmly and evenly into the bottom of the prepared pan. Bake for 10 minutes, then remove and let cool completely.
03 - Using an electric mixer, beat the softened cream cheese and sugar on medium speed until smooth and creamy. Add the eggs one at a time, beating well after each addition. Blend in the mashed bananas, vanilla extract, sour cream, and cornstarch until the mixture is fully incorporated and lump-free.
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 is just slightly wobbly when gently shaken.
05 - Turn off the oven and crack the door open slightly. Let the cheesecake cool in the oven for 1 hour to prevent cracking. Transfer to the refrigerator and chill for at least 3 hours, preferably overnight for the best texture.
06 - In a bowl, toss the sliced strawberries with the strawberry jam and lemon juice until evenly coated.
07 - Arrange the strawberry mixture over the top of the chilled cheesecake. Garnish with additional fresh banana and strawberry slices if desired. Slice into 10 portions and serve chilled.