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, granulated 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 minutes, then set aside to cool slightly.
03 - In a large bowl, beat softened cream cheese and granulated sugar together using an electric mixer until completely smooth and free of lumps. Add eggs one at a time, beating well after each addition. Stir in vanilla extract and sour cream until just combined — do not overmix.
04 - Pour the cheesecake filling over the partially cooled crust, using a spatula to spread it into an even layer.
05 - In a separate bowl, toss the diced peaches with granulated sugar and lemon juice. Evenly distribute the seasoned peaches over the cheesecake batter and gently press them in so they settle slightly into the filling.
06 - Bake for 30 to 32 minutes, or until the edges are set and lightly golden while the center still has a slight jiggle. The filling will continue to set as it cools.
07 - Allow the cheesecake to cool completely at room temperature, then transfer to the refrigerator and chill for at least 2 hours until firm and well set.
08 - In a chilled bowl, beat heavy whipping cream with powdered sugar using an electric mixer until soft peaks form. Be careful not to overwhip.
09 - Use the parchment overhang to lift the chilled cheesecake out of the pan. Slice into 12 even bars and top each with a dollop of whipped cream before serving.