Preheat oven to 300 degrees F (150 degrees C). Rinse the beef completely and pat dry.
Place the brisket on rack in a roasting pan or Dutch oven. Rub the brown sugar on the corned beef to coat entire beef, including the bottom. Pour the bottle of stout beer around, and gently over the beef to wet the sugar.
Cover, and place in preheated oven. Bake for 2 1/2 hours. Allow to rest 5 minutes before slicing.