Preheat oven to 300º F.
Rinse 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 stout beer or water mixture gently around and over the beef to dampen the sugar. Cover, place in preheated oven. Bake for 2½ hours.
During the last hour, you may put vegetables in the roasting pan. Try a wedge of cabbage, new potatoes, onion, carrots, etc. You may need to add a little more beer with your vegetables.
Remove; slice brisket thinly across grain (let it cool 5- 10 minutes for easier slicing). Serve with vegetables.