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 bowl until evenly moistened. Press the mixture 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 - Beat softened cream cheese and sugar together in a large bowl until smooth and creamy. Add eggs one at a time, mixing well after each addition. Blend in vanilla extract and sour cream until fully incorporated.
04 - Toss diced peaches with sugar, lemon juice, and cornstarch in a separate bowl until coated. Spread the peach mixture evenly over the cheesecake batter in the pan.
05 - Pour the cheesecake filling evenly over the cooled crust, smoothing the top with a spatula. Spread the prepared peach layer over the batter.
06 - Bake for 30 to 35 minutes until the center is set with only a slight jiggle. Remove from the oven and cool to room temperature. Refrigerate for at least 3 hours or until fully chilled throughout.
07 - Whip heavy cream with powdered sugar until soft peaks form. Drizzle or pipe over the chilled bars. Cut into 12 even squares and serve.