French onion soup is a quintessential dish of comfort and tradition: slow-simmered onions, a deeply savory broth, and a bubbly, browned cheese crust. This recipe sticks to the classic method while keeping the steps straightforward, so you can achieve that glossy caramelization and rich flavor at home.
What you'll need
Ingredients
- 4 large yellow onions, thinly sliced
- 2 tablespoons unsalted butter
- 1 tablespoon olive oil
- 1 teaspoon sugar (optional, for deeper caramelization)
- 2 tablespoons all-purpose flour
- 6 cups beef broth (or 4 cups beef plus 2 cups chicken/vegetable broth for a lighter version)
- 1/2 cup dry white wine or dry sherry
- 2 bay leaves
- 4-5 thyme sprigs (or 1 teaspoon dried thyme)
- Salt and freshly ground pepper to taste
- 1 baguette, sliced into rounds
- 8 ounces Gruyère cheese, grated (a mix with Swiss works too)
- Optional: splash of Cognac or good brandy (1-2 tablespoons)
Equipment (optional tips)
A heavy-bottomed pot or Dutch oven is ideal for even caramelization. Oven-safe bowls or crocks are handy for finishing under the broiler.
How to make
Step-by-step
-
In a heavy pot, melt the butter with the olive oil over medium heat. Add the onions and a pinch of salt. Cook slowly, stirring every few minutes, until they become deeply browned and caramelized (about 30-40 minutes). If using sugar, add it about halfway through to encourage browning.
-
Sprinkle the flour over the onions and stir for 1-2 minutes to make a light roux. This helps thicken the soup slightly and gives body to the finished dish.
-
If you’re using Cognac or brandy, you can add it now and let it cook for a minute to burn off the alcohol and mellow the taste. Otherwise, proceed to deglazing with the wine: pour in the wine and scrape up any browned bits from the bottom of the pot. Let the wine reduce by about half.
-
Add the beef broth along with the bay leaves and thyme. Bring to a gentle simmer and cook for 20-30 minutes, allowing the flavors to meld. Taste and season with salt and pepper, removing the bay leaves and thyme stems before serving.
-
While the soup simmers, prepare the bread: preheat the oven or a toaster oven to a high heat. Lightly brush baguette rounds with a touch of oil and toast until crisp and pale gold.
-
When you’re ready to serve, ladle the hot soup into oven-safe bowls. Top each bowl with a toasted bread round or two, then pile on the grated Gruyère cheese. Place the bowls under a hot broiler until the cheese melts and turns bubbly and golden, watching closely to prevent burning.
-
Serve the bowls hot, with extra bread on the side if desired. If you prefer a lighter finish, skip the broiler and simply melt the cheese in a conventional oven at a lower temperature until soft and creamy on top.
Tips and variations
Flavor tweaks
- Caramelization is the backbone of flavor here; take your time with the onions. A deeper browned color yields a richer soup.
- For a lighter broth, balance beef with vegetable or chicken stock, or use a 50/50 mix. A splash of white wine can be replaced with a touch of vermouth if you like.
- If you don’t have Cognac or brandy, a little extra wine or broth works fine; the key is deglazing well to lift the fond from the pot.
- To deepen aroma, add a sprig of thyme directly in the pot during simmering and remove before serving.
Variations
- Vegetarian version: use a rich vegetable stock or a mushroom-based stock. Sauté mushrooms with the onions for added depth.
- Onions: yellow onions are traditional for their sweetness, but a mix of yellow and red onions can provide extra complexity.
- Cheese options: Gruyère is classic, but a mix of Gruyère and fontina or Swiss also melts beautifully and tastes great.
Make-ahead and storage
- The soup improves with a bit of rest; refrigerate once cooled and reheat gently to avoid breaking the emulsions.
- Cheese toppings are best added just before serving. Leftover soup can be stored for 3-4 days in the refrigerator.
- Freezing is possible without the cheese components; store the soup base separately and reassemble with fresh bread and cheese when reheating.
Serving and storage
Serving suggestions
A crisp, well-toasted bread slice is essential. The cheese should form a thin, bubbling crust that melts into the soup below. A light garnish of chopped herbs, if you like, adds a touch of color.
Storage and leftovers
Store any leftovers in a sealed container in the refrigerator. Reheat gently on the stove, adding a splash of broth if the soup thickens too much. Re-crisp the croutons and re-cheese when reheating for the best texture.
Conclusion
French onion soup is a humble dish with a powerful effect: slow-cooked onions, a rich, savory broth, and a satisfying finish of toasty bread and cheese. With these steps, you can recreate that classic French comfort at home, any night of the week.