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 - In a medium bowl, combine graham cracker crumbs, granulated sugar, and melted butter. Mix until the crumbs are evenly coated and resemble wet sand. Press the mixture firmly and evenly into the bottom of the prepared pan. Bake for 8 to 10 minutes until lightly golden. Remove and let cool slightly.
03 - In a large bowl, use an electric mixer to beat the softened cream cheese and granulated 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.
04 - Pour the cheesecake batter evenly over the cooled crust, using a spatula to spread it into a smooth, level layer.
05 - In a separate bowl, toss the diced peaches with granulated 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 - Cover the pan and refrigerate for at least 3 hours, or until the bars are completely chilled and firm throughout.
08 - Use the parchment overhang to lift the dessert from the pan. Cut into 12 even bars. Whip the heavy cream with powdered sugar until soft peaks form, then drizzle or pipe over the bars before serving.