01 - Preheat oven to 350°F. Line a 9×9-inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.
02 - In a medium bowl, combine graham cracker crumbs, sugar, and melted butter. Mix until the crumbs are evenly coated and resemble wet sand. Press the mixture firmly into the bottom of the prepared pan in an even layer. Bake for 8 to 10 minutes until lightly golden. Set aside to cool slightly.
03 - Using an electric mixer, beat the softened cream cheese and sugar on medium speed until completely smooth and creamy, about 2 minutes. Add the eggs one at a time, mixing well after each addition. Blend in the vanilla extract and sour cream until fully incorporated. Pour the batter evenly over the cooled crust.
04 - Toss the diced peaches with sugar, lemon juice, and cornstarch until evenly coated. Spoon the peach mixture over the cheesecake layer, spreading it into an even distribution across the surface.
05 - Bake for 30 to 35 minutes, or until the center is just set with a slight jiggle remaining. Remove from the oven and allow to cool completely at room temperature.
06 - Cover and refrigerate for at least 3 hours, or until fully chilled and firm. Use the parchment overhang to lift the slab from the pan, then cut into 12 even bars.
07 - In a chilled bowl, whip the heavy cream with powdered sugar using an electric mixer until soft peaks form. Drizzle or pipe over individual bars before serving.