01 - Preheat oven to 350°F. Line a 9x9-inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.
02 - Combine graham cracker crumbs, sugar, and melted butter in a medium bowl 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 cream cheese and sugar on medium speed until completely smooth and creamy. Add the eggs one at a time, mixing thoroughly after each addition. Blend in the vanilla extract and sour cream until just combined.
04 - Pour the cheesecake batter evenly over the partially cooled crust, spreading with a spatula to create a smooth surface.
05 - Toss the diced peaches with sugar, lemon juice, and cornstarch in a bowl until evenly coated. Spoon and spread the peach mixture in an even layer over the cheesecake batter.
06 - Bake for 30 to 35 minutes until the center is set with only a slight jiggle when gently shaken. Remove from the oven and allow to cool completely at room temperature.
07 - Refrigerate the cheesecake bars for at least 3 hours or until fully chilled and firm throughout.
08 - Lift the slab from the pan using the parchment overhang and cut into 12 even bars. Whip the heavy cream with powdered sugar to soft peaks and drizzle or pipe over each bar before serving.