Step 1

Melt butter in a large pot over medium heat. Add onions and cook, stirring frequently, until caramelized (about 40 minutes).

Step 2

Add garlic and cook for another minute.

Step 3

Pour in wine, and scrape any browned bits off the bottom of the pot.

Step 4

Add beef broth, bay leaves, and thyme. Season with salt and pepper.

Step 5

Bring to a boil, then reduce heat and simmer for 30 minutes.

Step 6

Preheat the oven broiler.

Step 7

Ladle soup into oven-safe bowls. Top each with a slice of toasted baguette and a generous amount of Gruyère.

Step 8

Broil until cheese is bubbly and golden brown.