Peel, wash and slice the carrots. Peel, wash and chop the potatoes. Peel and finely chop the onion. Heat oil in a pan with lid. Fry the onion in it.
Add the potatoes and carrots and sauté briefly. Dust vegetables with flour and sauté briefly. Add stock while stirring and cook covered for about 15 minutes. Wash fish, dab dry and cut into medium-sized cubes.
Sprinkle with lemon juice. Season with salt and pepper. Wash the dill, pluck the flags and cut finely. Add cream to vegetables. Stir in horseradish. Bring to the boil. Add fish cubes, capers and dill and let it simmer at medium heat for about 5 minutes.
Season to taste again if necessary.