Cut off and discard wing tips. Divide wings in 2 pieces; set aside. To prepare sauce, melt butter and saute onion. Add mustard, sugar, vinegar, hot pepper sauce, Worcestershire sauce, ketchup, celery salt, cayenne and 1.5 cups beef broth. Bring to a boil. Meanwhile combine cornstarch with remaining half cup beef broth. Stir into boiling mixture and simmer 15 minutes. Barbecue wings over medium heat for 20 to 30 minutes, baste with sauce and continue to cook until tnder (approx. 20 minutes). Makes 4 to 6 servings.