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French Onion Soup Recipe With Gruyère Crust

French onion soup recipe with deeply caramelized yellow onions, savory beef broth, and a bubbling Gruyère crust. Toasted baguette slices soak up the rich soup before a quick broil turns the cheese golden.
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Prep Time 20 minutes
Cook Time 1 hour 34 minutes
Resting time 5 minutes
Total Time 1 hour 59 minutes
Servings: 6 servings
Course: Dinner
Cuisine: French
Calories: 540
Ingredients Equipment Method Notes

Ingredients
  

For the soup
  • 4 lb yellow onions thinly sliced
  • 3 tbsp unsalted butter
  • 1 tbsp olive oil
  • 1 tsp kosher salt plus more to taste
  • 2 cloves garlic minced
  • 2 tbsp all-purpose flour
  • 1 cup dry white wine
  • 2 carton (32 oz) low-sodium beef broth
  • 6 thyme fresh sprigs
  • 1 bay leaf
  • 0.5 tsp black pepper
For the Gruyère crust
  • 6 baguette 3/4-inch-thick slices, about 6 ounces total
  • 12 oz Gruyère cheese grated

Equipment

  • 1 7-quart Dutch oven
  • 1 rimmed baking sheet
  • 6 16-ounce broiler-safe bowls

Method
 

Make the soup
  1. Melt the butter and olive oil in a 7-quart Dutch oven over medium heat.
  2. Add the onions and salt and cook, stirring often, until softened, 10 to 15 minutes.
  3. Reduce the heat to medium-low and cook the onions uncovered, stirring frequently, until deeply golden and greatly reduced, 40 to 50 minutes.
  4. Stir in the garlic and cook for 30 seconds.
  5. Stir in the flour and cook for 1 minute.
  6. Pour in the wine, scraping up the browned bits, and simmer until reduced by about half, 3 to 5 minutes.
  7. Add the broth, thyme, bay leaf, and black pepper.
  8. Bring to a boil, then reduce the heat and simmer uncovered for 25 to 30 minutes.
  9. Remove the thyme stems and bay leaf, then taste and add more salt if needed.
Toast the bread
  1. While the soup simmers, heat the oven to 425°F.
  2. Arrange the baguette slices on a rimmed baking sheet and bake, turning once, until crisp and lightly golden, 8 to 10 minutes.
Assemble and broil
  1. Set an oven rack about 6 inches below the broiler and heat the broiler to high.
  2. Ladle the soup into six 16-ounce broiler-safe bowls.
  3. Place one toasted bread slice on each bowl.
  4. Top evenly with the Gruyère.
  5. Set the bowls on the baking sheet and broil until the cheese is bubbling and browned, 2 to 4 minutes, watching closely.
  6. Let rest for 5 minutes before serving.

Notes

For deeply golden onions, keep them cooking uncovered and stir frequently so they caramelize evenly. Refrigerate leftover soup for 3 to 4 days; freeze the soup without the bread and cheese for up to 3 months. For a gluten-free version, use gluten-free flour and baguette.