In 4-qt. saucepan or Dutch oven, saute mushrooms and onion in butter. Remove from pan into another container and set aside. In 4-qt. saucepan bring broth, barley, Worcestershire sauce and pepper to a boil; reduce heat. Cover and simmer 40 minutes, stirring occasionally. Add reserved mushrooms and onion along with parsley. Continue simmering 10 to 15 minutes or until barley is tender. Combine 1/2 cup milk, and flour, mixing until well blended. Gradually stir into soup along with remaining milk; heat through. Stir in sherry. Season to taste with salt. Additional milk or water may be added to to make soup the desired consistency.