Place dried mushrooms in bowl, cover them with water, soak 1/2 hour. Strain and reserve water.
Coarsely chop the reconstituted mushrooms.
Melt the margarine or butter in a stockpot and sauté the onion, celery, 2 tablespoons of the parsley, carrot, garlic, and fresh mushrooms until soft, about 5 minutes.
Lower the heat and add the flour, stirring every 30 seconds for about 5 minutes or until thick.
In a soup pot, heat the broth or water. Add a cup of mushroom mixture at a time to the pot, stirring.
Turn the heat to high, and add the reserved mushroom water and barley. Stir well and add salt to taste.
Simmer, covered, for about an hour or until the barley is tender and the soup is thick, stirring often.
Add additional chopped parsley, mix thoroughly, and adjust seasonings.
Garnish with a dollop of Greek yogurt and sprinkle with chopped fresh parsley.
Serve.
Before eating, stir in the yogurt well for a creamy tang.