8 tablespoons butter
2 cups sliced celery
1 cup sliced shallots
3/4 cup chopped onion
3 garlic cloves, minced
3 cups sliced stemmed fresh shiitake mushrooms
1 1/2 cups sliced crimini mushrooms
1 1/2 cups sliced white mushrooms
3 cups sliced oyster mushrooms
1/2 cup dry white wine
1/2 cup dry Sherry
1/4 cup all purpose flour
8 cups chicken stock
1/2 cup whipping cream
Melt 6 tablespoons butter in large pot over medium-high heat. Add celery, shallots, onion and garlic and sauté about 8 minutes. Add all mushrooms and sauté until beginning to soften, about 4 minutes. Add white wine and Sherry. Boil until liquid is reduced to glaze, about 6 minutes.
Mix remaining 2 tablespoons butter and 1/4 cup flour in small bowl until smooth paste forms. Add flour paste to mushroom mixture in pot; stir until mixture melts and coats vegetables. Gradually mix in stock. Bring to boil, stirring frequently. Reduce heat to medium-low and simmer until mushrooms are tender, stirring often, about 10 minutes. Stir in cream. Season with salt and pepper.
Working in batches, puree soup in blender or processor until smooth. Return soup to pot. (Can be prepared 1 day ahead. Cover and refrigerate. Rewarm over medium-low heat before serving.) Ladle soup into bowls and serve.
Makes 8 to 10 servings.