- Clean the fish and poach it with water, salt, one cleaned and roughly chopped onion and four carrots, washed parsley, mace, thyme and peppercorns.
- Let it poach slowly for 30 minutes.
- Clean the mussels one by one, remove the mud mussels, the broken mussels and the mussels that are open and do not close when touched.
- Wash the mussels several times in cold water.
- Sieve the fish stock, bring it back to the boil and cook the mussels in it for 8 minutes.
- Drain the mussels well and collect the cooking juices.
- Clean and chop the rest of the carrots and onions, celeriac and potatoes.
- Wash the celery and finely chop it.
- Heat the butter and slowly fry the vegetables.
- Add the stock and the mussels.
- Bring the soup to the boil and season to taste.
- If necessary, thicken the soup with some mixed flour.
- Stir the cream through the soup just before serving.
- Serve the soup with white bread and butter.