01 - Preheat oven to 325°F. Line a 9x9-inch baking pan with parchment paper, allowing excess to overhang for easy removal.
02 - Combine graham cracker crumbs, granulated sugar, and melted butter in a medium bowl. Press the mixture firmly and evenly into the base of the prepared pan to form a compact crust.
03 - In a large bowl, beat the cream cheese and sugar together until completely smooth and creamy. Add eggs one at a time, blending well after each addition. Mix in vanilla extract and sour cream until the filling is thoroughly blended.
04 - Pour the cheesecake filling onto the crust and spread it evenly. Bake in the preheated oven for 40 to 45 minutes, until the center is just set and the edges are lightly golden.
05 - Remove the baking pan from the oven and allow to cool completely at room temperature. Transfer to the refrigerator and chill for at least 3 hours, until fully set.
06 - Scatter an even layer of chopped strawberries and blueberries over the chilled cheesecake. Drizzle with melted white chocolate if desired. Cut into bars and serve well chilled.