Step 1: Preheat Oven

1. Preheat the oven to 325°F (160°C). Grease a 9-inch springform pan.

Step 2: Prepare the Chocolate Cookie Crust

1. In a medium bowl, combine the chocolate cookie crumbs, granulated sugar, and melted butter. Mix until well combined.
2. Press the mixture firmly into the bottom of the prepared springform pan to form an even layer. Bake for 10 minutes, then remove from the oven and let cool.

Step 3: Make the Cheesecake Filling

1. In a large mixing bowl, beat the softened cream cheese until smooth and creamy.
2. Gradually add the granulated sugar, mixing until well combined. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
3. Add the melted chocolate and cocoa powder, blending until smooth. Mix in the sour cream until fully combined.

Step 4: Bake the Cheesecake

1. Pour the cheesecake filling over the cooled crust and spread evenly.
2. Bake for 60–70 minutes, or until the center is set but still slightly jiggly. Turn off the oven and leave the cheesecake inside for 1 hour.
3. Remove from the oven and let cool at room temperature for about 30 minutes, then refrigerate for at least 4 hours, preferably overnight.

Step 5: Prepare the Chocolate Ganache

1. Heat the heavy cream in a small saucepan over medium heat until it begins to simmer.
2. Remove from heat, add the chocolate, let it sit for 1 minute, then stir until smooth and glossy.

Step 6: Assemble and Serve

1. Pour the chocolate ganache over the chilled cheesecake and spread evenly.
2. Carefully remove the sides of the springform pan, slice, and serve chilled.