Slice the onions thinly. Melt butter in a large pot over medium-low heat. Add onions and cook, stirring occasionally, until deeply caramelized (about 30-40 minutes). Add a pinch of salt and sugar to help the process.
Stir in flour and cook for 1 minute. Gradually whisk in beef broth, then add thyme, bay leaf, salt, and pepper. Bring to a simmer and cook for 15 minutes.
Preheat broiler. Slice baguette into 1-inch thick rounds and toast lightly.
Ladle soup into oven-safe bowls. Place a toasted baguette slice on top of each bowl and cover with grated Gruyère cheese.
Broil until cheese is melted and bubbly, about 2-3 minutes. Watch carefully to avoid burning.
Let cool slightly and serve immediately. Garnish with fresh parsley, if desired.
Enjoy this warm, comforting, and flavorful French Onion Soup!
Please sir, I want some more! This soup is fantastic. The best French onion soup I've ever had. Highly recommended.
A most agreeable soup. The flavors were well-balanced, and the cheese provided a delightful contrast in textures. I would certainly make it again.
A truly classic dish, executed perfectly. The slow caramelization of the onions is key, as the recipe suggests. Excellent!
Magnifique! This recipe is a winner. The broth was divine, and the Gruyère cheese on top was so wonderfully bubbly and brown. A perfect winter warmer.
Very good recipe. The flavors are fantastic, and the cheese topping is perfect. A little bit of salt and pepper would make it perfect.
