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

In a mixing bowl, combine chocolate wafer crumbs with melted butter and press it firmly into the bottom of the prepared springform pan. Bake for about 10 minutes until set and fragrant. Let cool completely.

Melt bittersweet chocolate using a double boiler over low heat. Stir until smooth and remove from heat to cool slightly.

Blend full-fat cream cheese in a food processor until creamy. Gradually add granulated sugar, light brown sugar, and cocoa powder until fully incorporated.

With the processor running, add large eggs and egg yolks one at a time, followed by heavy cream. Blend until smooth.

Fold melted bittersweet chocolate and vanilla extract into the cream cheese mixture. Pour over cooled chocolate crust and smooth the top.

Place the springform pan into a larger baking dish and fill with hot water up to 1 inch high. Bake for 1 hour and 10 minutes or until edges are set and center jiggles slightly.

Let the cheesecake cool on a wire rack for 30 minutes at room temperature. Chill in the fridge for at least 6 hours or overnight.

In a saucepan, simmer the heavy cream until warm, then stir in chopped semi-sweet chocolate until melted. Mix in unsalted butter for extra richness, if desired. Let cool slightly.

Pour chocolate ganache over the chilled cheesecake, spreading evenly. Let set for at least 1 hour in the refrigerator before slicing and serving.