01 - Preheat oven to 325°F (160°C). Lightly grease a 9-inch (23 cm) springform pan and line the bottom with parchment paper.
02 - In a mixing bowl, combine 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 raspberries, granulated sugar, and lemon juice. Cook over medium heat, stirring occasionally, until the raspberries soften and break down, approximately 5 minutes. Stir in the cornstarch slurry and continue to simmer for 2-3 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 white chocolate using a double boiler or microwave in short intervals; allow it to cool slightly. In a large mixing bowl, beat the softened cream cheese and granulated sugar with an electric mixer until smooth and creamy. Incorporate the eggs one at a time, mixing thoroughly after each addition. Stir in the vanilla extract, sour cream, and all-purpose flour. Finally, fold in the cooled melted white chocolate until fully combined.
05 - Pour half of the cheesecake batter over the prepared crust. Drizzle half of the cooled raspberry sauce over the batter and gently swirl it with a knife to create a marbled pattern. Carefully pour the remaining cheesecake batter over the swirled layer, then drizzle the remaining raspberry sauce on top and swirl again for an elegant marbled finish.
06 - Bake for 50-60 minutes, or until the edges are set and the center remains slightly wobbly. Turn off the oven, prop the door ajar, and allow the cheesecake to cool within the oven for 1 hour.
07 - Remove the cheesecake from the oven and transfer it to the refrigerator to chill for a minimum of 4 hours, or ideally, overnight, to fully set.
08 - Carefully remove the cheesecake from the springform pan. Slice and serve chilled.