For the Crust:

1. Arrange your oven racks so that one is in the middle of the oven and one is below that. Preheat oven to 350°F. Butter a 9-inch spring form pan with butter and line the bottom with a round of parchment paper. Place the spring form pan on a baking sheet.
2. In a food processor, process the chocolate wafers until fine crumbs form. Add in the sugar and pulse to combine. With the machine running, slowly stream in the butter and process until the mixture resembles wet sand.
3. Pour the mixture into the prepared spring form pan and press down evenly to form a compact layer. Set aside.

For the Filling:

1. In a pot over medium high heat, add the chopped chocolate and the beer. Stir until melted and then remove from heat. Allow to cool.
2. Place the cream cheese and sugar in the bowl of stand mixer. Turn on the mixer and blend until the cream cheese is fluffy. With the machine running, crack in the eggs, one at a time, and mix until smooth and incorporated. Beat in the vanilla bean paste/extract. Pour in the cooled chocolate-beer mixture and beat until well combined.
3. Whisk together the cocoa powder, flour, espresso powder, and salt in a mixing bowl. Gradually add to the cream cheese mixture, a little at a time, and mix on low speed until just combined.
4. Pour the batter into the pan with the prepared crust. Place the baking sheet with the spring form pan into the preheated oven on the middle rack. Place a baking dish on the lower rack of the oven and carefully fill with warm water.
5. Bake for 40-45 minutes or until the center of the cheesecake is set. Remove from the oven and set aside.

For the Topping:

1. Add the ingredients to a bowl and whisk until well combined. Top the cheesecake with the sour cream topping and return to the oven for 8 minutes. Remove cheesecake from the oven, allow to cool to room temperature, and then transfer the whole pan to the fridge to chill for at least 3 hours (longer is even better!). Before serving, grate the dark chocolate over top and slice.