Advent Day 7 - French Onion Soup

It was chilly here again today, so another good soup is in order. This is another great recipe from my mom and is delicious.

French Onion Soup
1 large onion, thinly sliced
1 tablespoon butter or margarine
2 cans condensed beef broth(look for low sodium)
1 1/2 cups water
1 to 2 tablespoon sherry (or you can sub. apple juice, apple cider, red wine vinegar, or chicken broth)
1/2 teaspoon Worcestershire sauce
dash of pepper
croutons
6 tablespoons grated cheese(mozzarella or whatever you like)

Melt the butter in a pot and cook the onion on low heat for 20 minutes. Add the rest of the ingredients(except the croutons and cheese) and bring to a boil. Put into oven-proof bowls(individual servings), top with croutons and cheese. Broil to melt cheese. Serve with crusty bread.