mushrooms thoroughly, pour cold water over them, and keep that
way for 5Ч 8 hours. Transfer into some other vessel and pour the
same liquid (preliminarily strained through a piece of
cheese-cloth) over them. Cook on low heat until soft. Wash the
cooked mushrooms with hot water and chop fine. Make a flour
dressing from 2 or 3 tablespoons of flour and 1 spoon of butter.
Separately heat the finely chopped onion until light yellow.
Slightly chill and dilute the flour dressing with the mushroom
liquid. Boil, stirring and skimming the scum. Put the chopped
mushrooms and onion in the sauce, salt, pepper, and boil for
another 5Ч10 minutes.
You can add sour cream to the sauce, in which case the mushrooms
are cooked in a lesser amount of water.