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French Onion Soup

This classic French Onion Soup features slowly caramelized yellow onions transformed into a rich, sweet, and smoky base through patient, low-heat cooking. Topped with toasted baguette slices and melted Gruyère cheese, the final dish boasts a deeply savory, bubbling crust with tender, jammy onions inside, creating a comforting, layered texture.
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Prep Time 15 minutes
Cook Time 1 hour
Total Time 1 hour 15 minutes
Servings: 4
Course: Main Course
Cuisine: French
Calories: 350
Ingredients Equipment Method Notes

Ingredients
  

  • 4 large yellow onions thinly sliced
  • 2 tablespoons butter for caramelization
  • 1 tablespoon oil neutral oil like vegetable or canola
  • 1/4 cup dry white wine optional, for lift and brightness
  • 4 cups beef broth or vegetable/mushroom broth for vegetarian
  • 2 sprigs fresh thyme or 1 tsp dried thyme
  • 1 baguette sliced into rounds about 1/2-inch thick
  • 1 1/2 cups Gruyère cheese grated

Equipment

  • Heavy-bottomed pot
  • Sharp Knife
  • Cutting board
  • Baking sheet
  • Oven-safe bowls or crocks
  • Wooden spoon

Method
 

  1. Peel and thinly slice the onions, aiming for about 1/8-inch slices. This helps them caramelize evenly and develop a rich flavor.
  2. Heat the butter and oil in a heavy-bottomed pot over medium-low heat until melted and fragrant. Add the sliced onions and a pinch of salt, stirring to coat them evenly in the fat.
  3. Cook the onions slowly, stirring every 10 minutes, until they turn a deep golden brown and become jammy, about 45-60 minutes. Keep the heat low to avoid burning and add a splash of water if they start sticking.
  4. Once caramelized, pour in the white wine and increase the heat slightly. Let it simmer until the wine reduces by half, about 5 minutes, to lift the sweet onion flavors.
  5. Add the broth, thyme, and bay leaf. Bring to a gentle simmer and cook uncovered for 20 minutes to meld all the flavors. Taste and season with salt and pepper as needed.
  6. Preheat your oven to 200°C/390°F. Slice the baguette into rounds and toast on a baking sheet until crispy and golden, about 8 minutes.
  7. Remove the herbs from the soup and ladle it into oven-safe bowls. Top each with a toasted baguette slice, then sprinkle generously with grated Gruyère cheese.
  8. Place the bowls on a baking sheet and broil in the oven until the cheese is bubbling and golden, about 3-5 minutes. Keep a close eye to prevent burning.
  9. Carefully remove the bowls from the oven and let sit for 1-2 minutes. The cheese will be hot and gooey, with a crispy edge, ready to serve.

Notes

Patience during caramelization is key to developing the deep, smoky flavor. For vegetarian versions, substitute mushroom or vegetable broth and skip the wine if desired.