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 set aside to cool completely.
03 - Using an electric mixer, beat the softened cream cheese and sugar together on medium speed until completely smooth and free of lumps.
04 - 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 batter is fully combined and silky.
05 - Pour the filling over the cooled crust and smooth the surface with a spatula. Bake for 50 to 60 minutes, until the center is just set with a slight wobble remaining.
06 - 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 for the best set.
07 - Toss the sliced strawberries with strawberry jam and lemon juice in a bowl until evenly coated. Arrange the mixture over the top of the chilled cheesecake.
08 - Garnish with additional fresh banana and strawberry slices if desired. Slice into wedges and serve chilled.