Heat the oil in a large saucepan over medium heat. add the celery, onion and potatoes and sauté until tender, about 5-10 minutes.
Add the fish and continue cooking for 2-3 minutes. Add the garlic, thyme and bay leaves. Add the fish stock, tomato paste and peppers.
Bring the soup to the boil, lower to a simmer and cook for 30 minutes. Add the prawns and salt and papper to taste. Continue cooking for about 2 minutes, just until the prawns lose their translucence.
Servings: 4 to 6