1. Rinse the dried mushrooms. Place each variety of dried mushrooms in 2 cups of cold water and soak for at least 4 hours or overnight. 2. In a large pot, bring the stock to a simmer. Add the celery, onions, and carrots. Strain the dried mushrooms, reserving the soaking liquid. Add the strained soaking liquid to the soup. Chop the hydrated mushrooms into 1/4-inch pieces slightly larger than the diced vegetables and add to the soup. Add the sliced white button mushrooms. 3. Cover and cook the soup until the vegetables are tender, about 60 minutes. Bring the soup to a boil. Stirring constantly, add the orzo. Reduce the heat to a gentle boil and, stirring occasionally to prevent the pasta from sticking, cook until the orzo is cooked through, another 6 to 8 minutes. 4. Meanwhile melt the butter in a small saucepan over medium heat. Add the flour and cook, stirring constantly until smooth, 3 to 5 minutes. Remove 1 cup of the broth from the soup and add to the roux, whisking constantly until slightly thickened and free of lumps. Stir the thickened liquid into the soup. Add the chopped parsley and dill. 5. Finish the soup with sour cream: Add 1/4 cup of the thickened soup to the sour cream. Whisk until smooth. Add the sour cream to the soup, whisking constantly until it is well incorporated, about 3 minutes. Season to taste with salt and pepper. Recipe by: Martha Stewart Posted to recipelu-digest Volume 01 Number 302 by James and Susan Kirkland on Nov 24, 1997