Preheat your oven to 325°F (163°C). Grease a 9-inch springform pan with butter, then wrap the outside in aluminum foil.

In a mixing bowl, combine chocolate wafer crumbs with melted unsalted butter and press into the bottom of the springform pan. Bake for 10 minutes.

Set up a double boiler and melt chopped bittersweet chocolate, then allow it to cool slightly.

Blend full-fat cream cheese in a food processor until smooth. Add granulated sugar, light brown sugar, and unsweetened cocoa powder; blend until combined.

With the processor running, add the large eggs and heavy cream. Blend until combined.

Fold the cooled melted chocolate and vanilla extract into the cream cheese mixture, and pour over the cooled crust.

Place the springform pan in a larger roasting pan. Pour hot water into the larger pan until about 1 inch up the sides of the springform pan.

Bake for 1 hour and 10 minutes until edges are set and center is slightly jiggly.

Allow the cheesecake to cool on a wire rack for about 1 hour, then refrigerate for at least 6 hours or overnight.

For the ganache, heat heavy cream until boiling and pour over chopped semi-sweet chocolate, whisk until smooth.

Pour ganache over the chilled cheesecake, allow to set at room temperature for about 1 hour.

Run a warm knife around edges of springform pan, release sides and slice into neat pieces.