Classic French Onion Soup Gratinée

Preparation

1. 1Melt butter in a large heavy-bottomed pot or Dutch oven over medium heat.
2. 2Add the sliced yellow onions, sprinkle with salt, and cook, stirring occasionally, until deeply caramelized and very tender, about 30-40 minutes. Lower heat if onions are browning too quickly.
3. 3Pour in the dry white wine and scrape up any browned bits from the bottom of the pot. Let it simmer until the wine has mostly evaporated, about 5 minutes.

Cooking the Soup

1. 1Stir in the beef broth and fresh thyme (if using). Bring the soup to a simmer and cook for at least 20 minutes to allow the flavors to meld. Season with salt and pepper to taste.
2. 2Preheat your oven's broiler. Arrange the baguette slices on a baking sheet and toast until golden brown.
3. 3Ladle the hot soup into oven-safe crocks or bowls. Place 2-3 toasted baguette slices on top of each bowl of soup, ensuring they are slightly submerged but still expose some surface for cheese.
4. 4Generously sprinkle the shredded Gruyère cheese over the baguette slices.
5. 5Place the soup crocks under the preheated broiler for 3-5 minutes, or until the cheese is bubbling and golden brown. Watch carefully to prevent burning.

Serving

1. 1Carefully remove the hot crocks from the broiler using oven mitts. Let stand for a few minutes before serving as the bowls will be very hot.
2. 2Serve hot and enjoy the rich, savory flavors of this classic French dish.