PUT DRIED MUSHROOMS in small dish. Add boiling water. Set aside to soak. Heat oil in 4-quart pot. Add onions. Cook over medium heat until softened, about 5 minutes, stirring often. Add celery root, half of mushrooms, pear and 4 cups stock. Bring to boil. Simmer, covered, until celery root is soft, about 25 minutes. Thinly slice remaining mushrooms. Set aside. Strain solids from liquid, reserving both. Strain dried mushrooms from liquid, reserving both.
Puree solids and dried mushrooms in processor or in batches in blender until completely smooth. Return to pot. Stir in cooking and mushroom liquid, remaining stock and mushroom slices. Simmer, covered, 10 minutes. Stir in cream, and water to thin soup if necessary (it should be very thick). Adjust seasoning. Heat through but do not boil. Can be refrigerated as long as 4 days or frozen up to 3 months. Serve hot. Makes 11 Cups