Clean the mullets. Mince the parsley, celery and garlic and sauté in a saucepan with 2 oz. olive oil. When the vegetables are tender, add the tomatoes and cook for 10 mins. Remove from heat and set aside.
Coat the fish with flour and fry in oil in a saucepan till golden brown on both sides. Add salt and pepper to taste. Grease a casserole with oil, place the mullets in it, and pour the sauce in the casserole with the fish and bake for 5 more mins. at 450ºF.
Serve with a generous, sprinkling of chopped parsley.