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, stirring until the mixture resembles wet sand. Press firmly and evenly into the bottom of the prepared pan. 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 in a large bowl until completely smooth and free of lumps. Add eggs one at a time, mixing well after each addition. Blend in vanilla extract and sour cream until fully incorporated.
04 - In a separate bowl, toss the diced peaches with sugar, lemon juice, and cornstarch until evenly coated. Spread the peach mixture in an even layer over the cheesecake batter.
05 - Pour the cheesecake filling evenly over the cooled crust. Bake for 30 to 35 minutes, or until the center is set with only a slight jiggle remaining. Remove from the oven and allow to cool completely at room temperature.
06 - Refrigerate the cheesecake bars for at least 3 hours, or until thoroughly 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 until soft peaks form. Drizzle or pipe the whipped cream over the bars just before serving.