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 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 softened cream cheese and sugar in a large bowl until completely smooth and free of lumps. Add eggs one at a time, beating well after each addition. Blend in vanilla extract and sour cream until just combined — do not overmix.
04 - Pour the cheesecake filling over the cooled crust and spread into an even layer. In a separate bowl, toss diced peaches with sugar and lemon juice. Scatter the peaches evenly over the batter and gently press them in.
05 - 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 cool completely at room temperature.
06 - Refrigerate the cheesecake for at least 2 hours, or until fully chilled and firm throughout.
07 - Beat heavy whipping cream with powdered sugar using an electric mixer until soft peaks form. Keep chilled until ready to serve.
08 - 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 if desired.