With a sharp knife, cut six 1-in.-long slits in meat; insert a garlic clove half into each slit. Combine the brown sugar, salt and pepper; rub over roast., In an ovenproof Dutch oven over medium heat, brown roast in oil on all sides. Add the onion, beef consomme, Worcestershire sauce, mustard, bay leaf and browning sauce if desired., Cover and bake at 350° for 1-3/4 to 2-1/4 hours or until meat is tender. Remove roast to a serving platter; keep warm., Discard bay leaf. Add the mushrooms, beer and thyme to the pan. Bring to a boil over medium-high heat. Cook until liquid is reduced by half. Combine cornstarch and water until smooth; gradually stir into pan. Bring to a boil; cook and stir for 2 minutes or until thickened. Serve with roast.