4 tablespoons butter
3 cloves garlic, finely chopped
2 fresh bay leaves
2 tablespoons finely chopped fresh thyme
Salt and pepper
1 cup dry white wine
1 quart beef stock
2 tablespoons Worcestershire sauce
1 baguette, ends trimmed, sliced into 16 rounds about an inch thick
1/2 pound Gruyere cheese, shredded
4 tablespoons good quality dry sherry, optional
Heat a heavy soup pot over medium heat while thinly slicing the onions. Add butter to the pot and melt. Add onions, garlic, bay leaves, thyme, salt and pepper, and gently caramelize, stirring frequently, 30 minutes. If the onions begin to brown to quickly at edges before they caramelize, turn heat down a bit. Deglaze the pan with the wine, let reduce a minute while stirring. Add stock and Worcestershire sauce and simmer 15 minutes more.
Meanwhile, place rack in middle of oven, heat oven to 250F.
Place a cooling rack over a baking sheet and arrange the bread slices on it. Toast bread 15 minutes. Switch broiler on. Top the bread with lots of mounded cheese and broil 2-3 minutes to melt cheese.
Ladle soup in shallow bowls and stir in a tablespoon of sherry per bowl, if using. Set 4 cheesy croutons into each bowl and serve.