Peel, wash and cut the potatoes into pieces. Peel and chop the onions. Peel and chop the carrots. Heat oil in a pot. Fry the potatoes, onions and carrots.
Deglaze with the stock, bring to the boil and cook for about 25 minutes. Clean and wash the leek and cut into rings. Cook in boiling salted water for about 5 minutes and drain. Mix crème fraîche and horseradish.
Cut salmon into strips. Wash the dill and cut finely. Puree soup and add leek. Season to taste with salt, pepper and cayenne pepper. Arrange potato soup with crème fraîche, salmon and dill in bowls.