Preheat your oven to 350°F and lightly grease a 9-inch springform pan.

Combine the crushed cookies with melted butter and press the mixture into the bottom of the pan to form a crust. Bake for 8 minutes, then set aside to cool.

In a large bowl, beat the cream cheese and sugar until smooth. Add sour cream, cocoa powder, and vanilla extract, mixing until well combined.

Add eggs one at a time, fully incorporating each before adding the next. Scrape down the sides of the bowl as needed.

Gently fold in the melted chocolate until the mixture is uniform.

Pour the filling over the prepared crust and smooth the top with a spatula.

Bake for 50-55 minutes, or until the edges are set but the center is still slightly jiggly.

Turn off the oven, open the door slightly, and let the cheesecake cool in the oven for 1 hour to prevent cracking.

Remove the cheesecake from the oven and refrigerate for at least 4 hours, or overnight, until fully set.

Serve chilled with a dollop of whipped cream, if desired.