Creamy Onion Soup

1 pound yellow onions (about 3 medium) -- sliced

2 tablespoons butter or margarine

4 cups chicken broth

dash pepper dash dried thyme 1/4 teaspoon salt -- optional

2 cups milk -- divided

1/3 cup all-purpose flour

In a 3-qt. saucepan over medium heat, saute onions in butter. Add broth, pepper, thyme and salt if desired; bring to a boil. Reduce heat; cover and simmer for 20 minutes. Add 1 2/3 cups milk. Stir flour into remaining milk until smooth; add to soup. Bring to a boil; boil and stir for 2 minutes or