To start preheat the oven to 350 degrees. Grease a 8-inch springform pan.
On the stove top over medium heat in a small pan heat the butter until melted then add 1 cup of beer. Turn off the heat then add the cocoa powder, sugar and brown sugar. Set aside to cool.
In another smaller bowl add the eggs sour cream, vanilla then stir to combine. Now in a larger bowl add the dry ingredients: flour, salt and baking soda.
Once the butter & beer has cooled down add to the dry ingredients. Then add the sour cream & eggs to that. Add to the pan.
Bake the cake for 45-55 minutes depending on your oven.
Take out of the oven and then use a knife to scrape the sides of the pan to release the cake from the sides then flip open the springform pan. Put the cake on a cooling rack or plate and let the cake cool fully.
Use one tub of mascarpone cheese and add sugar and vanilla until completely combined. Spread over the top of the cake.