Rinse eel with cold water. Oil baking pan with half of the oil. Place slices of eel on pan. Sauce: Heat remaining oil in frying pan, and fry onions and garlic on medium heat for 5 minutes. Add remaining ingredients and cover. Cook 10 minutes. Pour sauce over eel. Bake 45 minutes at 375 degrees. Serve with crusty bread and a crisp salad.