Preheat your oven to 325°F (163°C). In a mixing bowl, combine chocolate wafer crumbs and melted unsalted butter until well blended. Press this mixture into the bottom of a greased 9-inch springform pan. Bake for 10 minutes until set, then remove and let it cool completely.

Set up a double boiler to melt the bittersweet chocolate, stirring until smooth. In a food processor, blend cream cheese, granulated sugar, light brown sugar, and cocoa powder until creamy. Add eggs, heavy cream, and vanilla, mixing until fully incorporated. Fold in melted chocolate.

Pour the cheesecake filling over the cooled crust in the springform pan. To create a water bath, place the pan in a larger baking dish and fill with hot water halfway up the sides. Bake for 1 hour and 10 minutes until slightly jiggly in the center.

Once baked, carefully remove the cheesecake from the water bath and run a knife around the edges to prevent cracking. Allow it to cool completely at room temperature. Refrigerate for at least 6 hours.

Heat heavy cream in a saucepan until simmering. Pour hot cream over chopped chocolate in a bowl and let sit for a minute. Whisk until smooth, creating a ganache.

Once the cheesecake has chilled, pour the ganache over the top, spreading it evenly. Let it set at room temperature for 1 hour before serving.