Soak cod in water for 2 to 3 days, refrigerated, changing water every day. In large casserole, heat oil and add onion and celery. Saute until golden brown. Add olives. Add white wine. Reduce by half. Stir in tomatoes and broth. Bring to a boil. Lower to simmer. Add potatoes and cod and cook until cod breaks off with a fork and the potatoes are tender. Taste, add parsley and season with salt and pepper. Serve hot.
Salt may not be necessary.