01 - Preheat oven to 325°F (163°C). Line a 9x9-inch baking pan with parchment paper, ensuring an overhang for easy bar removal.
02 - Combine graham cracker crumbs, granulated sugar, and melted butter in a medium bowl. Press mixture firmly and evenly into the bottom of the prepared pan.
03 - In a large bowl, beat softened cream cheese and granulated sugar with an electric mixer until smooth and creamy. Add eggs one at a time, mixing thoroughly after each addition. Blend in vanilla extract and sour cream until fully incorporated.
04 - Pour the cheesecake batter evenly over the crust. Bake for 40 to 45 minutes, or until the edges are lightly golden and the center is just set.
05 - Remove from oven and allow to cool completely to room temperature. Refrigerate for at least 3 hours, or until fully chilled.
06 - Top chilled cheesecake evenly with chopped strawberries and blueberries to create a festive design. Drizzle with melted white chocolate if desired.
07 - Using the parchment overhang, lift bars from the pan. Cut into equal portions and serve chilled.