1 Cut the leeks lengthwise, thoroughly rinse, trim and cut into thin rings. Peel the potatoes, celery and parsley root, rinse and cut into small, bite-sized pieces.
2 Peel the onion and garlic, chop finely and sweat until translucent in a pan with melted butter. Put in the vegetables, sauté briefly and pour in the broth. Season with salt and pepper, and simmer for about 15 minutes over medium heat.
3 Take half of the diced vegetables from the soup, puree the soup and put the diced vegetables back in. Separate the fish into pieces, put in the soup, leave to soak for about 5 minutes, season to taste and serve garnished with parsley.