01 - Preheat oven to 325°F. Line a 9x9-inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.
02 - In a medium mixing bowl, combine graham cracker crumbs, granulated sugar, and melted butter. Mix until fully combined, then press the mixture evenly into the bottom of the prepared pan to form a compact base.
03 - In a large bowl, beat the softened cream cheese and granulated sugar with an electric mixer on medium speed until smooth. Add eggs one at a time, mixing after each addition. Blend in vanilla extract and sour cream until just combined and creamy.
04 - Spread the cheesecake batter evenly over the prepared crust. Bake in the preheated oven for 40 to 45 minutes, or until the edges appear lightly golden and the center is just set.
05 - Remove from oven and allow to cool to room temperature in the pan. Once cooled, refrigerate for a minimum of 3 hours to fully set.
06 - Once chilled, top evenly with chopped strawberries and blueberries. Drizzle with melted white chocolate if desired for a decorative finish.
07 - Using the parchment paper overhang, lift the bars out of the pan. Slice into 16 squares and serve chilled for optimal texture.