1. Preheat oven to 325°F (160°C). Grease a 9-inch springform pan and line the bottom with parchment paper.

2. In a bowl, mix chocolate cookie crumbs, melted butter, and sugar. Press mixture firmly into the bottom of the pan and chill while preparing the filling.

3. In a saucepan, combine blueberries, sugar, and lemon juice. Cook over medium heat until berries burst. Stir in cornstarch slurry and simmer until thickened. Cool completely.

4. In a large bowl, beat cream cheese and sugar until smooth. Add eggs one at a time, then mix in sour cream, vanilla, and lemon juice until creamy. Add black food coloring if desired.

5. Pour cheesecake batter into prepared crust. Drop spoonfuls of blueberry sauce on top and swirl gently with a knife to create a marbled effect.

6. Bake for 55–65 minutes, until the center is just set. Turn off the oven, crack the door, and let the cheesecake cool inside for 1 hour.

7. Refrigerate for at least 4 hours or overnight.

8. Top with extra blueberry sauce, fresh berries, or a drizzle of dark glaze before serving.