Preheat oven to 325°. Dredge beef pieces in flour; brown a few at a time in hot oil and place in large ovenproof casserole. Add onions and garlic to oil in pan and  brown lightly. Place in casserole. Add sugar, 2 tablespoons wine vinegar, parsley, bay leaves, thyme, salt and pepper. Stir once or twice. Pour off any remaining oil in skillet. Put in broth and heat over low flame, stirring to loosen all browned bits. Pour over mixture in casserole. Add beer. Cover casserole and bake 2 hours. Stir in 2 remaining tablespoons wine vinegar. Keep hot on top of stove until ready to serve.