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French Onion Soup

French Onion Soup is a comforting dish featuring slow caramelized onions simmered in a rich broth, topped with toasted baguette slices and melted Gruyère cheese. The key to its depth of flavor is patience during the slow caramelization process, which develops a smoky sweetness and complex aroma. The final dish boasts a velvety broth with a bubbling, golden cheese crust and crisp bread topping, creating a harmonious blend of textures and flavors.
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Prep Time 15 minutes
Cook Time 1 minute
Total Time 1 minute
Servings: 4
Course: Main Course
Cuisine: French
Calories: 320
Ingredients Equipment Method Notes

Ingredients
  

  • 4-5 large yellow onions peeled and thinly sliced
  • 2 tbsp butter unsalted
  • 1 tbsp olive oil
  • ½ cup dry white wine optional, for deglazing
  • 1.5 liters beef broth or vegetable broth for vegetarian
  • 2 sprigs fresh thyme
  • to taste salt & pepper
  • 4 slices baguette about 1 cm thick, toasted
  • 1 ½ cups Gruyère cheese grated, enough to cover toppings generously

Equipment

  • Wide, heavy-bottomed pot
  • Wooden spoon
  • Sharp knife
  • Baking sheet
  • Ovenproof bowls

Method
 

  1. Peel and thinly slice the onions evenly, aiming for uniform strips that will caramelize uniformly.
  2. Heat a wide, heavy-bottomed pot over medium-low heat and add the butter and olive oil. Once melted and fragrant, add the sliced onions and stir to coat them thoroughly.
  3. Cook the onions slowly, stirring every 10-15 minutes, until they soften and begin to turn translucent, filling the kitchen with a sweet aroma.
  4. Continue cooking and stirring patiently as the onions deepen in color, turning to a rich amber over about 45 minutes. The slow caramelization releases their natural sweetness and smoky notes.
  5. Once caramelized, pour in the white wine to deglaze the pan, scraping up all the browned bits from the bottom. Let the wine simmer for 2 minutes to cook off the alcohol.
  6. Add the beef broth, thyme sprigs, and season with salt and pepper. Bring the mixture to a gentle simmer and cook uncovered for 20-30 minutes to meld the flavors.
  7. While the soup simmers, toast the baguette slices in a preheated oven at 180°C (356°F) until golden and crispy, about 10 minutes.
  8. Remove the thyme sprigs from the soup and taste, adjusting salt and pepper as needed for a balanced flavor.
  9. Ladle the hot soup into ovenproof bowls, then top each with a toasted bread slice and a generous handful of grated Gruyère cheese.
  10. Place the bowls on a baking sheet and broil in the oven until the cheese bubbles and turns a golden brown, about 2-3 minutes. Watch closely to prevent burning.
  11. Remove the bowls from the oven, let them sit for a minute for the cheese to settle, then serve hot, garnished with extra thyme or pepper if desired.

Notes

Patience during caramelization is key to developing the soup's deep flavor. For a vegetarian version, substitute beef broth with vegetable broth and ensure the cheese is vegetarian-friendly. To prevent sogginess, toast the bread slices until very crisp before adding to the hot soup. Broil the cheese just until bubbly and golden for the perfect crust.