Make sure your ingredients are at room temperature and preheat oven to 350 degrees F.

In a small bowl, mix the graham cracker crumbs, cocoa powder, sugar, and melted butter together. Press mixture into the bottom of a 9-inch spring form pan.

Melt the chocolate and cream together in a double boiler or in the microwave (1 minute, stirring once in the middle). Stir to combine completely and allow to cool slightly.

In a large bowl, beat the cream cheese until creamy with an electric mixer. Mix in the melted chocolate mixture, sugar, sour cream, eggs, and vanilla until completely combined. Mix in the Guinness until it is fully incorporated.

Pour the cheesecake filling into the spring form pan. Bake for 60 minutes. Turn off heat and leave cheesecake in the oven with the door slightly ajar for 60 minutes.

Let cake cool completely on the counter and then chill the cheesecake in the fridge (uncovered) for at least 6 hours (I like to leave mine overnight).

To make the glaze, place the chopped chocolate and cream in a small non-stick pot over medium-low heat. Bring to a simmer and whisk until a smooth ganache forms. Remove from the heat and whisk in the butter until completely incorporated. Pour the glaze in an even layer over the chilled cheesecake. Chill cheesecake thoroughly.

To serve, carefully unmold the sides of the springform. Run a sharp knife under hot water to warm the blade, and wipe dry with a towel. Slice cleanly, wiping the blade between slices and reheating as necessary. Serve chilled