Peel and cut the carrot, onion, leek and celery into pieces.

Put the vegetables, peppercorns and fish offal into the water and bring to a boil. Let it simmer for approx. 20 minutes, while skimming off the foam that forms on top.

While the stock is boiling, prepare the ingredients for the soup.

Fish balls: Chop the fish into small pieces with a knife.

Mix together fish pieces, potato flour and salt in a baking bowl or using a food processor.

Whisk in milk until you have a smooth, airy mass.

Boil lightly salted water. Shape the fish mince into small balls with a teaspoon. Drop these into the water and let soak for approx. 5 minutes until the fish balls are firm.

The soup: Cut the vegetables the way you like them best, either in thin sticks or in small pieces.

When the stock is ready, strain it through a colander or a kitchen towel. Add the vegetables and cream to the stock and bring to a boil. Mix the vinegar into the sour cream.

Turn down the temperature on the plate, and add the sour cream mixture to the soup while whisking well.

Put the fish balls in the soup. Cut the fish into pieces and add them. Smooth the soup with a little flour and season with salt and pepper. Let the fish soak in the soup for about 5 minutes.

Put the soup in large deep plates, sprinkle over the prawns and serve the soup with fresh bread.