Firstly, sauté the chopped onions in the butter and add the pre-soaked mushrooms (1 hour). Add the stock and the water from the mushrooms, the potatoes cut into cubes and the spices. After a short time add marinated mushrooms and boil until the mushrooms and potato cubes are soft. Dilute the sour cream with the milk, mix in the flour and thicken the soup. Allow to simmer for 10 minutes and add a little sugar and dill. Add the sliced eggs but do not boil any more. No need to make the soup any sourer; the marinated mushrooms give it a wonderful taste and the dried mushrooms a great smell.