Sauté onions in butter in a Dutch oven over medium heat 15 minutes or until golden, stirring often. Stir in flour; cook one minute. Add water and next 8 ingredients. Bring to a boil; reduce heat and simmer, partially covered 30 minutes. Discard bay leaves.
Ladle soup into 4 individual oven-proof soup bowls. Place on a baking sheet. Add 2 bread slices to each bowl and cover with 2 slices cheese. Broil 5 1/2 inches from heat 2 minutes or until cheese is bubbly. Serve immediately.