This is a typical soup in the Krkonose Mountains and the adjacent regions. It is made of bread yeast and served at almost all restaurants in the Krkonose region of the Czech Republic.
Pour lukewarm water on the bread yeast, mix and add salt and caraway. Let it warm until the next day. Add the broth from the soaked mushrooms and the chopped mushrooms. Cook over medium heat for approx. half an hour, until the soup becomes thick. Add finely chopped onion fried in butter, and not too thick a mix of beaten eggs. Before serving the soup, add peeled and sliced potatoes that have been boiled in the skin.
Source: Regionální turistické informační centrum Krkonoše