Polish Mushroom Soup (Zupa Grzybowa)
This beloved mushroom soup is traditionally made with Polish borowik mushrooms and is served on Christmas Eve. Dried porcini, cepes or boletes make a very close substitute and are readily available any time of the year.
Of course, there are a many versions of this soup as there are Polish cooks (and their numerous descendants). Here is our recipe, which we think is a very nice version indeed.
Place the dried mushrooms in a bowl and cover with warm water. Soak for 20 - 30 minutes, or until the mushrooms are softened and pliable.
Coarsely chop the fresh mushrooms. Heat the butter in a large pot over medium heat. Add the onions and sauté for 5-7 minutes until softened and translucent. Add the chopped fresh mushrooms and sauté for another 15 minutes.
Add the stock and bring to a low boil. Strain the reconstituted dried mushrooms, reserving the soaking liquid. Rinse the strained mushrooms briefly under cold running water to remove any traces of grit. Carefully decant the strained soaking liquid into the soup, making sure to exclude any remaining grit or debris. Chop the reconstituted mushrooms coarsely and add to soup.
Cover and reduce the heat to a low simmer and continue to cook for about an hour.
Whisk the flour into sour cream until smooth and lump free. Temper the sour cream/flour mixture by gradually adding about 1 cup of the hot soup to the sour cream, mixing constantly until smooth. Now pour the sour cream mixture slowly to the pot, stirring constantly. Reduce heat to low and simmer for five minutes, stirring occasionally. Add salt & pepper to taste and stir in 3 tablespoons of the dill.
Serve garnished with the remainder of the chopped dill.