Clean all the different types of fish well, especially the squid or cuttlefish. Boil the cod, the skate and the heads off the red mullet and the soles in about half a litre of lightly salted water, in which you have put the pepper, bay leaves and juniper berries. After about 15 minutes of cooking time, remove the heads off the cod and the skate and cut the flesh into small pieces and put them to one side. Strain the cooking stock and keep it on the heat. Boil the prawns and keep just the tails.
Heat 3 spoonfuls of oil, as soon as it gets hot, add the finely chopped celery, carrot, parsley, garlic and onion. When the vegetables are browned, pour over the white wine. Evaporate the wine, then add the fish stock and the tomatoes. Season with salt and pepper, after this, add the chopped squid or cuttlefish. After about 40 minutes put in the sole, skinned and cut into small pieces, also the chopped mullet. After another 20 minutes, throw in the prawn tails. To finish off, add the cod and the skate. After 2 or 3 minutes the soup is ready. Serve with croutons.