Preheat your oven to 325°F (163°C) and grease a 9-inch springform pan thoroughly.

In a mixing bowl, combine chocolate wafer crumbs with melted unsalted butter until well mixed. Press evenly into the bottom of the pan. Bake for 10 minutes, then allow to cool.

Chop bittersweet chocolate and melt it in a heatproof bowl over a double boiler, stirring until smooth for 5-7 minutes. Set aside to cool.

In a food processor, blend cream cheese until creamy. Gradually add granulated sugar, light brown sugar, and cocoa powder until incorporated.

With the processor running, add eggs and heavy cream until combined. Avoid over-mixing.

Fold in the melted chocolate and vanilla extract. Pour this filling over the cooled crust.

Place the springform pan in a larger baking pan and fill the outer pan with hot water about 1 inch up the sides of the springform.

Bake for 1 hour and 10 minutes until the center jiggles slightly but is mostly set.

Let cool in the pan for about an hour before refrigerating for at least 6 hours or overnight.

To make the ganache, simmer heavy cream until just boiling and pour over chopped chocolate. Whisk until smooth and stir in unsalted butter.

Spread the cooled ganache over the cheesecake. Let it set for about 30 minutes before slicing.