Step 1: Preheat oven to 350°F (175°C). In a medium bowl, combine graham cracker crumbs, sugar, and melted butter. Press the mixture firmly into the bottom of a 9-inch springform pan. Bake for 8-10 minutes. Remove from oven and let cool. Reduce oven temperature to 325°F (160°C).
Step 2: In a large bowl, beat softened cream cheese and sugar with an electric mixer until smooth and creamy. Beat in eggs one at a time, mixing until just combined. Stir in vanilla extract and mashed bananas. Do not overmix.
Step 3: Pour the banana cheesecake filling over the cooled crust. Place the springform pan in a larger roasting pan. Carefully pour hot water into the roasting pan until it reaches about halfway up the sides of the springform pan.
Step 4: Bake for 60-70 minutes, or until the edges are set but the center still jiggles slightly. Turn off the oven, crack the door open, and leave the cheesecake inside for 1 hour to cool gradually.
Step 5: Remove from oven, remove from water bath, and let cool completely on a wire rack. Once cool, cover and refrigerate for at least 4 hours, or preferably overnight, before adding the topping.
Step 6: In a small saucepan, combine sliced strawberries, sugar, and lemon juice. Cook over medium heat, stirring occasionally, until strawberries soften and release their juices (about 5-7 minutes).
Step 7: Stir in the cornstarch slurry and continue to cook, stirring constantly, until the mixture thickens (about 1-2 minutes). Remove from heat and let cool completely.
Step 8: Once the cheesecake is chilled and the strawberry topping is cool, spread the strawberry topping evenly over the top of the cheesecake. Carefully remove the sides of the springform pan. Slice and serve.