In large covered saucepan, cook onions in butter over low heat for about 30 minutes, stirring ocassionally

Add beef broth, water and worcestershire sauce. Heat to boiling. Reduce heat. Cover and simmer for 30 minutes

Place toasted bread in each bowl. Pour hot soup over bread and cover with cheese. Cheese will melt in about a minuteor you can put it under the broiler to brown the cheese.