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, ¼ cup granulated sugar, and melted butter. Mix until the crumbs are evenly moistened. Press the mixture 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 ⅔ cup granulated sugar in a large bowl until completely smooth and creamy. Add the eggs one at a time, beating well after each addition. Blend in the vanilla extract and sour cream until just combined — do not overmix.
04 - Pour the cheesecake filling over the cooled crust, using a spatula to spread it into an even layer.
05 - In a separate bowl, toss the diced peaches with 2 tablespoons sugar and lemon juice. Distribute the peach pieces evenly over the cheesecake batter and gently press them in.
06 - Bake for 30 to 32 minutes, or until the edges are lightly golden and the center is set but still has a slight jiggle. Avoid overbaking — the bars will continue to set as they cool.
07 - Cool the cheesecake completely at room temperature, then refrigerate for at least 2 hours until thoroughly chilled and firm.
08 - In a chilled bowl, beat the cold heavy whipping cream with powdered sugar using an electric mixer until soft peaks form.
09 - Lift the chilled cheesecake from the pan using the parchment overhang. Slice into 12 bars and top each with a dollop of whipped cream before serving.