Preheat the oven to 325°F (160°C).

In a mixing bowl, combine the chocolate graham cracker crumbs, melted butter, and sugar.

Press the crust mixture firmly into the bottom of a 9-inch springform pan.

Bake the crust in the preheated oven for about 10 minutes.

In a large mixing bowl, beat the softened cream cheese until smooth.

Add the granulated sugar and vanilla extract to the cream cheese, mixing until well combined.

Add the eggs one at a time, mixing well after each addition.

Stir in the sour cream until smooth.

Gently fold in the melted chocolate until fully incorporated.

Pour the filling over the baked crust and smooth the top.

Bake for about 60 minutes or until the edges are set and the center slightly jiggles.

Allow the cheesecake to cool at room temperature for an hour, then refrigerate for at least 4 hours or overnight.