Preheat your oven to 350°F (175°C) and prepare your springform pan by lightly greasing the sides.

Combine chocolate graham cracker crumbs, melted unsalted butter, and granulated sugar in a medium bowl. Press mixture into the bottom of the prepared springform pan and bake for about 10 minutes.

In a large mixing bowl, beat softened cream cheese until creamy. Gradually add sour cream and heavy cream, mixing until smooth.

Incorporate cocoa powder and granulated sugar slowly into the mixture on low speed until blended.

Blend in eggs one at a time, mixing on low until just incorporated.

Pour the filling into the cooled crust and bake for 55-65 minutes until slightly jiggly in the center.

Turn off the oven, leave the cheesecake inside with the door ajar for about 1 hour to cool gradually.

Heat heavy cream in a small saucepan until simmering. Pour over chopped dark chocolate and let sit for 5 minutes, then stir until smooth.

Spread the ganache over the cooled cheesecake and refrigerate for at least 4 hours before serving.

Carefully run a knife around the edges before releasing the cheesecake and slice to serve.