Remove skin from fish and cut into large cubes about 1 inch per side.
Cut celery into very small cubes.
Cut carrot, onion and potato into small cubes of approx 1cm or 2cm to your liking.
Optionally you can add a piece of smoked bacon to give more flavor. After sautéing the vegetables, it will be discarded.
Sauté the onion and the potato together with the oil and a tablespoon of butter over high heat for approx. 2 minutes.
When the onion is starting to turn transparent add the carrot and celery.
Optionally you can add a halved clove of garlic to be able to remove it later along with the lime and bay leaf.
Add a little salt and cook over medium heat for a few minutes.
It is very important to verify that the potato is still hard. Do not overcook. It has to stay hard.
When the potato can be cut with a knife but still using some force (it is still hard) add the broth
Add half a lime and a few bay leaves and bring back to a boil over medium heat.
Add the salmon and cod and cook over medium/low heat for approx 5 minutes.
If the prawns are raw, add them now.
In order not to stop the cooking, preheat the cream and then add it. Bring to a boil again over low heat. (Remember that when boiling the cream rises and can overflow. Be careful if the saucepan is covered so that this does not happen).
If the prawns were precooked add them now.
Check the salt and if necessary add more.
Cook until potato and fish are done. It is important that both vegetables and fish are not overcooked. They have to be "al dente".
To slightly thicken the soup:In a bowl, dilute two tablespoons of flour in hot broth and add them to the soup with a fine strainer to avoid lumps.(Add more flour if you prefer it thicker.) When it is ready, let it rest for a few minutes.
It can be decorated with parsley or dill.
That's it. Enjoy!