This classic French onion soup recipe offers a warm, comforting meal perfect for chilly evenings.
Caramelizing the onions slowly develops deep, sweet flavors that define the soup's character.
Topped with toasted bread and melted Gruyère cheese, this soup makes a satisfying appetizer or main dish.
Why You’ll Love This Recipe
- Slow caramelization of onions creates rich, sweet flavors essential for authentic French onion soup.
- Using a good quality beef broth enhances the soup's depth and heartiness.
- Toasting the bread and melting Gruyère cheese on top adds texture and a luxurious finish.
Classic French Onion Soup with Gruyère Crust
A comforting Classic French Onion Soup featuring deeply caramelized onions, rich beef broth, and a golden Gruyère cheese crust toasted to perfection.
- Prep time
- 15 minutes
- Cook time
- 65 minutes
- Servings
- 4
- Yield
- 4 servings
Ingredients
- 6 large yellow onions, thinly sliced (about 4 cups)
- 4 tablespoons unsalted butter (60 g)
- 2 tablespoons olive oil (30 ml)
- 1 teaspoon salt
- 1/2 teaspoon sugar
- 4 cups beef broth (950 ml)
- 2 cups water (475 ml)
- 1/2 cup dry white wine (120 ml) optional
- 4 slices French baguette, about 1/2 inch thick
- 1 1/2 cups grated Gruyère cheese (170 g)
- Fresh ground black pepper to taste
- Chopped fresh thyme or parsley for garnish (optional)
Instructions
- Caramelize the onions In a large, heavy-bottomed pot or Dutch oven, melt the butter with olive oil over medium heat. Add the sliced onions, salt, and sugar. Cook, stirring frequently, until the onions are deeply golden brown and caramelized, about 45 minutes. Adjust heat as needed to prevent burning.
- Simmer the soup Add the white wine (if using) to the caramelized onions and cook for 2-3 minutes to reduce slightly. Pour in the beef broth and water. Bring to a simmer and cook for 15 minutes to meld flavors. Taste and adjust seasoning with salt and pepper.
- Prepare the bread and cheese While the soup simmers, preheat the oven to 400°F (200°C). Place baguette slices on a baking sheet and toast in the oven until golden, about 5-7 minutes. Remove and set aside.
- Assemble and gratinée Ladle the hot soup into oven-safe bowls. Place one or two toasted baguette slices on top of each bowl of soup. Generously sprinkle grated Gruyère over the bread. Place the bowls on a baking sheet and broil in the oven until the cheese is golden brown and bubbly, about 3-5 minutes. Watch closely to prevent burning.
- Serve Carefully remove the bowls from the oven using oven mitts. Garnish with fresh thyme or parsley if desired. Serve immediately.
Helpful Tips
- Use low to medium heat when caramelizing onions to avoid burning and achieve a sweet, deep flavor.
- If you prefer a vegetarian version, substitute beef broth with a rich vegetable broth and omit the wine if desired.
- Be cautious while broiling the cheese; it can brown quickly, so stay near the oven.
- For best taste, use freshly grated Gruyère cheese rather than pre-shredded, which may not melt as well.
- This recipe contains common allergens: dairy (butter and cheese) and gluten (bread). Use lactose-free butter or cheese alternatives and gluten-free bread for dietary modifications.
Storage and Make-Ahead
Store leftover soup (without the bread and cheese topping) in an airtight container in the refrigerator for up to 3 days.
Reheat gently on the stove until steaming hot, at least 165°F (74°C) internal temperature for safe consumption.
Do not store soup with bread and cheese topping, as the bread will become soggy and cheese may spoil.
Frequently Asked Questions
Can I make French onion soup ahead of time?
Yes, you can make the soup base ahead and store it refrigerated for up to 3 days. Add the bread and cheese just before serving and broil to finish.
What bread works best for French onion soup?
French baguette sliced about 1/2 inch thick is ideal as it crisps up well under the broiler and holds the cheese nicely.
Can I use a slow cooker to make French onion soup?
Yes, caramelize onions on the stove first, then transfer to a slow cooker with broth and simmer for 2-3 hours for rich flavor development.
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