Remove the brisket from the packaging. If your package includes a seasoning packet, rub it on both sides. If it doesn't, don't worry. It will still have plenty of flavor.
Heat your smoker to 275F degrees. Place the brisket on the smoker, fat side up. Smoke until the internal temperature of the meat reaches 165F degrees. This can take 3-5 hours, depending on the size of your brisket.
Place two sheets of foil on the counter. Add 4 tablespoons of butter on the foil. Fold up the sides to form an edge. Carefully pour 1/3 cup of stout onto the butter. Add the brisket on top. Wrap tightly with both sheets of foil, locking in the liquid.
Return to the smoker until the internal temperature of the meat reaches 205F degrees.
While the brisket is smoking, make the beer glaze. Add all glaze ingredients to a saucepot and boil for 10-15 minutes, until reduced by half.
Remove the brisket from the foil. Slice into one-inch chunks. Place in an aluminum pan. Pour the beer glaze into the pan with any juices collected in the foil, and toss to coat.
Cover with foil, and return to the smoker for one hour.