Preheat oven to 325°F. Lightly grease a 9-inch springform pan and line with parchment paper.

To a medium saucepan, combine raspberries, water, sugar, and cornstarch. Cook over medium heat, stirring often, until the mixture thickens, about 20-25 minutes. Remove from heat and let cool.

Combine crushed Oreo cookies and melted butter. Press mixture into the bottom of the prepared pan. Wrap the bottom of the pan with foil to prevent leaks.

Melt chocolate chips with ¼ cup of heavy cream in the microwave until smooth. Let cool slightly.

In a mixing bowl, beat cream cheese until smooth. Add sugar and cocoa powder, mix well. Add eggs one at a time, then stir in remaining heavy cream and vanilla. Fold in melted chocolate.

Pour batter over the crust. Dollop cooled raspberry sauce on top, swirl gently with a skewer to create a marbled effect.

Place the springform pan into a larger pan, pour hot water into the larger pan about halfway up the sides of the springform. Bake for 100-105 minutes until the edges are set, center slightly jiggly.

Remove from oven, cool on a wire rack for 1 hour. Refrigerate for at least 4 hours or overnight before serving.

Garnish with fresh raspberries and chocolate shavings if desired. Serve chilled.