Make the Cake -  This portion of the recipe can be made ahead and allowed to sit at room temperature for 2 days

1. Preheat oven to 350º
2. Line twelve 3" diameter pastry rings with parchment paper that extends up the sides of the rings and above about 1". Make a bottom for the rings using tin foil. This cake batter is very wet, so the rings will leak if the bottom is not lined. Place prepared rings on a flat baking sheet. (If you do not have rings, you may use lined cupcake tins, or a 9” round cake pan with 3” sides, buttered & lined with parchment paper)
3. Melt the butter and Guinness in a large pot over medium-high heat. Whisk in the cocoas and sugar
4. In a separate bowl, over medium-high heat, whisk the sour cream, eggs and vanilla. Add to the butter mixture
5. Whisk in the remaining dry ingredients to blend, then pour into prepared rings (⅓ cup per ring) or pan. Bake for 20-25 minutes with rings or cupcake tins or 45-50 minutes in a cake pan. Test with toothpick for doneness
6. Cool thoroughly before removing from rings/pan

Prepare the Sabayon

1. In a stainless bowl, whisk yolks with the sugar and salt, then add liqueur and water
2. Place bowl over a simmering pot of a small amount of water and continue whisking until mixture has thickened, 2-3 minutes
3. Remove from heat and whisk in melted chocolate, then place bowl over an ice bath, whisking occasionally until the mixture has cooled, about 1-2 minutes
4. Fold in the whipped cream

Assemble

1. Press each cake (or a piece of cake) into a small, clear drinking glass
2. Top with sabayon. It will actually look like a pint of Guinness!