This recipe calls for 24 oz of stout, but the easiest bottle to buy for someone who does not want extra bottles of stout was the 22 oz Guinness. I just added a little extra water to the glaze. Note that this cake has 2 glazes: a hot stout-cocoa glaze that will soak into the cake and a thicker stout-cocoa-chocolate glaze that will drape over the cooled bundt.
Preheat the oven to 350 F.
Bring the 2 cups of stout to a boil in a medium-large saucepan (warning: beer boils over really easily! Keep a close eye on this!) and then lower heat to simmer for 20 minutes and reduce to 1 cup.
Add 2.5 oz chopped chocolate to reduced but hot stout. Stir to combine and then set aside to cool.
Beat the butter with a mixer (hand or stand) until creamy. Scrape the sides and bottom of the bowl and add the sugar in 3 additions, beating until fluffy and scraping in between additions.
Scrape the sides and bottom of the bowl. Add the eggs and beat in one at a time, scraping the sides and bottom of the bowl before each egg.
Whisk together the cocoa powder, flour, baking powder, baking soda and salt.
Mix the vinegar into the chocolate.
Alternate adding the flour mixture and chocolate mixture in 4 and 3 additions, beginning and ending with the flour mixture, on the lowest speed (you can also do this folding by hand but I am lazy and use a mixer).
Spray a 8-9 inch bundt pan with a flour-oil combo such as Baker's Joy.
Scrape the cake batter into the prepared pan and smooth the top. Bake for 40 minutes, or until a cake tester inserted into the center of the cake comes out clean.
Let cake cool in pan for 5-10 minutes, and then invert the cake onto a cooling rack. Place foil or wax paper under the cooling rack.
Be very careful when making this glaze--my stout boiled over!
Add the 1 cup of stout, 1 1/2 cups sugar, 1/4 cup cocoa powder and water to a medium saucepan. Whisk together on medium low heat.
Bring to a boil and then reduce heat to simmer, without stirring, for 10 minutes until the glaze thickens slightly.
Turn the heat off and remove 2/3 of the syrup to a bowl.
Add the 1 oz of chopped chocolate to the remaining stout mixture and whisk smooth.
Using a pastry brush, brush the hot cocoa-stout syrup all over the hot cake immediately after inverting. When the cake is brushed evenly all over, pour the remaining stout-cocoa syrup all over the cake.
Let the cake cool completely. Replace the wax or foil paper under the cooling rack with a clean piece. Whisk the stout-cocoa-chocolate syrup. If it is no longer pourable, heat it on low, stirring, until it is.
Let the syrup cool as much as it can and still be pourable. Pour the glaze all over the cake. If a lot drips down onto the wax/foil, you can pick it up, replace with more fresh, and squeeze it out to pour over the cake again. Repeat until all over the chocolate glaze has been used.
Let the glaze set completely before serving with freshly whipped cream.