Fry the prawns for a couple of minutes in olive oil, then fry the redfish and put both aside.
Put fish bones, white wine and water to a boil, skim off any foam, then simmer for 20 minutes. Never let a good stock cook more than 20 min.
Dice and sauté fennel, leek, onion, garlic and carrots in olive oil and thyme in a saucepan. Add the tomato puree and saffron. Sift the fish stock and pour onto the vegetables. Discard the bones. Season the soup with salt and pepper. Dice and add the tomato together with mussels and cod, cook for 2 minutes (until the clams open). Add redfish and prawns. Serve the soup smoking hot.