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, 1/4 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 2/3 cup granulated sugar in a large bowl on medium speed until completely smooth and free of lumps. Add the eggs one at a time, beating well after each addition. Stir 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 granulated sugar and lemon juice. Evenly distribute the peaches 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, transfer the pan to the refrigerator and chill for at least 2 hours, or until the cheesecake is firm and well set.
08 - In a chilled bowl, beat the heavy whipping cream with powdered sugar using an electric mixer until soft peaks form. Be careful not to overwhip.
09 - Lift the cheesecake slab out of the pan using the parchment paper overhang. Slice into 12 even bars. Top each bar with a dollop of freshly whipped cream before serving.