1-Preheat the oven to 325°F (163°C). Grease the bottom and sides of a 9-inch springform pan and wrap the outside with heavy-duty aluminum foil for a water bath.

2-Mix the chocolate wafer crumbs and melted butter in a bowl, press the mixture into the pan bottom, and bake for 10 minutes. Let it cool on a wire rack.

3-Melt the bittersweet chocolate using a double boiler: simmer water in a pot and place a heatproof bowl with the chopped chocolate over it, stirring occasionally until melted; set aside.

4-In a food processor or high-powered blender, blend the cream cheese until smooth, then add the granulated sugar, light brown sugar, and unsweetened natural cocoa powder, blending until smooth.

5-Add the eggs, egg yolks, and heavy cream, mixing until just combined. Fold in the melted chocolate and vanilla extract, pulsing to ensure even blending, and scrape the sides as needed.

6-Pour the filling over the cooled crust in the pan. Place the pan in a larger roasting pan, then add hot water to the roasting pan until it reaches about 1 inch up the side of the springform pan. Bake for 1 hour and 10 minutes, or until the center is set but slightly jiggly.

7-Remove the pan from the water bath and run a knife around the edge to prevent cracking. Cool completely in the pan at room temperature, then refrigerate for at least 6 hours before slicing.

8-For the ganache, heat the heavy cream to a simmer, pour half over the finely chopped semi-sweet chocolate, let it sit for 1 minute, and whisk until smooth. Gradually add the remaining heavy cream while whisking, then stir in the cubed unsalted butter until melted. Pour the ganache over the cooled cheesecake and let it set for about 1 hour before serving.

9-Slice the cheesecake with a clean, sharp knife for each cut.