In a large pot, melt the butter over medium heat. Add the sliced onions and cook, stirring frequently, until they are caramelized and golden brown, about 25-30 minutes.

Add Liquids and Seasoning

Once the onions are caramelized, add the dry white wine, beef broth, thyme, bay leaves, salt, and black pepper. Bring the mixture to a simmer and let it cook for about 20 minutes.

Prepare the Bread

While the soup is simmering, preheat your oven to 350°F (175°C). Place the baguette slices on a baking sheet and toast them in the oven until they are golden brown, about 10 minutes.

Assemble the Soup

Remove the bay leaves from the soup. Ladle the hot soup into oven-safe bowls. Top each bowl with a few slices of toasted baguette, followed by a generous layer of Comté, Gruyère, and Raclette cheese.

Broil the Cheese

Place the bowls under the broiler for about 5-7 minutes or until the cheese is bubbly and golden brown. Keep a close eye on it to prevent burning.

Serve

Remove from the oven and let cool slightly before serving. Enjoy your delicious onion soup with melted cheese!