French Onion Soup

INGREDIENTS

• 4 cups reduced-sodium beef broth (32 fl oz)
• 1 (1/2-lb) piece Gruyère, Comte, or Emmental
• 6 (1/2-inch-thick) diagonal slices of baguette
• 3/4 cup dry white wine
• 1/2 stick (1/4 cup) unsalted butter
• 3 sprigs fresh thyme
• 2 Turkish bay leaves or 1 California
• 2 teaspoons all-purpose flour
• 3/4 teaspoon salt
• 1 1/2 cups water
• 2 tablespoons finely grated Parmigiano-Reggiano
• 2 lb medium onions, halved lengthwise, then thinly sliced lengthwise
• 1/2 teaspoon black pepper