1 pound fresh mushrooms (I use Portobello), coarsly chopped
1 large onion, diced
4 tablespoons butter
juice of 1/2 lemon
1/4 cup water
6 cups rich beef broth or stock
1 cup sour cream
3 tablespoons flour
salt and pepper to taste
1/4 cup fresh dill, chopped for garnish if desired
Parsley for garnish if desired
In a large sauce pan, sauté onions in butter over medium heat for 5-7 minutes until softened, add mushrooms and sauté for another 15 minutes. Add lemon juice and water and cook covered for another an additional 5 minutes.
Transfer the mushroom and onion mixture to a soup pot and add in the broth. Bring to a low simmer. Blend the sour cream with the flour and mix well. Gradually add 1 cup of the hot soup to the sour cream and mix until smooth. Pour the sour cream mixture slowly to the pot, stirring constantly. Simmer for five minutes, stirring occasionally. Serve garnished with chopped dill or parsley.