Cut onions in half and then cut into slices. Sautee onions in a little oil. When onions are yellowish-clear, add mushrooms (use of mushroom depends on how much you like mushrooms). Keep on sautee until mushrooms are brown. Add onion soup mix and water to make a thick sauce. Move the mushrooms and onions to the side of pan, spread fish onto pan, cover the fish with the sauce and vegetables. Cover pan with lid and cook on low fire until fish is soft (10-15 minutes, check with fork).