Preheat your oven to 325°F (163°C). In a mixing bowl, combine chocolate cookie crumbs, melted unsalted butter, and sugar until evenly moistened. Press firmly into the bottom of a springform pan, then bake for 10 minutes or until set. Let it cool completely.

In a large mixing bowl, beat softened cream cheese and granulated sugar together until smooth. Gradually add unsweetened cocoa powder, incorporating each egg one at a time. Stir in vanilla extract, sour cream, and melted dark chocolate until fully combined.

Pour the cheesecake filling over the cooled crust, spreading it evenly. Bake for 55-60 minutes until the edges are set but the center slightly wobbles. Let cool inside the oven for 1 hour.

Prepare the cherry topping by combining cherries, sugar, and lemon juice in a saucepan. Cook until simmering, then mix cornstarch with water and stir into the cherry mixture. Cook for about 5 minutes until thickened, then cool.

Transfer the cheesecake to the refrigerator to chill for at least 4 hours. Top with cooled cherry mixture just before serving.