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, 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 cream cheese and sugar on medium speed until completely smooth and free of lumps. Add the eggs one at a time, mixing well after each addition. Blend in the vanilla extract and sour cream until just combined.
04 - Pour the cheesecake filling evenly over the cooled crust, using a spatula to spread it into a smooth, even layer.
05 - 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.
06 - Bake for 30 to 35 minutes, or until the center is set with only a slight jiggle when gently shaken. Remove from the oven and allow to cool to room temperature on a wire rack.
07 - Refrigerate the cheesecake bars for at least 3 hours, or until completely chilled and firm throughout.
08 - Whip the heavy cream with powdered sugar until soft peaks form. Drizzle or pipe over the chilled bars before slicing into 12 equal portions and serving.