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, 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 - Using an electric mixer, beat the softened cream cheese and sugar together in a large bowl until completely smooth and creamy. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract and sour cream until just combined, being careful not to overmix.
04 - Pour the cheesecake filling over the prepared crust, using a spatula to spread it into an even layer.
05 - In a separate bowl, toss the diced peaches with sugar and lemon juice until coated. Evenly distribute the peach pieces over the cheesecake batter and gently press them in so they are partially submerged.
06 - Bake for 30 to 32 minutes, or until the edges are set and lightly golden while the center still has a slight jiggle. Remove from the oven and allow to cool completely at room temperature.
07 - Once cooled to room temperature, refrigerate the cheesecake for at least 2 hours, or until thoroughly chilled and firm.
08 - If using the topping, beat the heavy whipping cream with powdered sugar in a chilled bowl until soft peaks form.
09 - Lift the chilled cheesecake from the pan using the parchment overhang. Slice into 12 even bars and top each with a dollop of whipped cream before serving.