01 - Preheat oven to 325°F (160°C). Lightly grease a 9-inch springform pan and line the bottom with parchment paper.
02 - In a medium bowl, combine the graham cracker crumbs, melted butter, and granulated sugar until thoroughly mixed. Firmly press the mixture onto the bottom of the prepared springform pan. Bake for 10 minutes, then allow to cool slightly.
03 - In a small saucepan, combine the fresh or frozen raspberries, granulated sugar, and lemon juice. Cook over medium heat for approximately 5 minutes, until the raspberries begin to break down. Stir in the cornstarch slurry and simmer for 2 to 3 minutes, until the sauce thickens. Strain the sauce through a fine-mesh sieve to remove seeds, then set aside to cool completely.
04 - Gently melt the chopped white chocolate using a double boiler or in a microwave, heating in short intervals. Allow the melted chocolate to cool slightly. In a large mixing bowl, beat the softened cream cheese and granulated sugar with an electric mixer until light and smooth. Incorporate the large eggs one at a time, mixing thoroughly after each addition. Stir in the vanilla extract, sour cream, and all-purpose flour until just combined. Finally, fold in the slightly cooled melted white chocolate until uniformly blended.
05 - Pour half of the prepared cheesecake batter over the cooled crust. Drizzle half of the cooled raspberry sauce over the batter, then gently swirl with a knife to create a marbled pattern. Carefully pour the remaining cheesecake batter over the first layer and repeat the swirling process with the remaining raspberry sauce.
06 - Bake the cheesecake for 50 to 60 minutes, or until the edges are set and the center is still slightly wobbly when gently shaken. Turn off the oven, prop the door open slightly, and allow the cheesecake to cool inside the oven for 1 hour.
07 - Carefully remove the cheesecake from the oven and transfer it to the refrigerator. Chill for a minimum of 4 hours, or ideally overnight, for best results.
08 - Once thoroughly chilled, remove the cheesecake from the springform pan. Slice into portions and serve cold.