Creating the Yummy Dark Chocolate Raspberry Cheesecake is straightforward if you follow these steps:

1. Preheat Oven: Preheat your oven to 325°F (163°C). Grease a 9-inch springform pan and set aside.
2. Prepare the Crust: In a medium bowl, mix chocolate cookie crumbs, melted butter, and granulated sugar until well combined. Press the mixture firmly into the bottom of the prepared springform pan.
3. Bake the Crust: Bake the crust in the preheated oven for 10 minutes. Remove and let cool while preparing the filling.
4. Make the Cheesecake Filling: In a large mixing bowl, beat the softened cream cheese and granulated sugar until smooth and creamy.
5. Add Cocoa and Eggs: Mix in the unsweetened cocoa powder, followed by the eggs, one at a time, ensuring each is fully incorporated before adding the next.
6. Incorporate Vanilla and Cream: Add the vanilla extract, sour cream, and heavy cream, mixing until just combined. Fold in the melted dark chocolate chips.
7. Pour Filling into Crust: Carefully pour the cheesecake filling over the cooled crust, smoothing the top with a spatula.
8. Bake the Cheesecake: Bake in the oven for 55-60 minutes, or until the center is set but still slightly jiggly.
9. Cool the Cheesecake: Turn off the oven and crack the door open. Let the cheesecake cool in the oven for 1 hour. Then, refrigerate for at least 4 hours or overnight to set completely.
10. Prepare Raspberry Topping: In a small saucepan, combine fresh raspberries, granulated sugar, lemon juice, and cornstarch (if using). Cook over medium heat until the raspberries break down and thicken slightly. Remove from heat and let cool.
11. Assemble the Cheesecake: Once the cheesecake is fully chilled, spread the raspberry topping evenly over the top.