French onion soup is a bistro classic, the most homey and delicious example of good cafe cooking. But only a handful of frugal ingredients make up this restaurant favorite. Onions, broth, salt, and butter mingle in a slow magic that transforms them into a wildly luxurious bowl of silky onions and dark broth. If you've only eaten French onion soup in restaurants you'll be shocked at how easy it is to make in your own kitchen.
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Here is a step-by-step recipe for making the best French onion soup you've ever eaten. It's one of the simplest yet most satisfying soups, and one to learn by heart.
The Magic Ingredient: Time
French onion soup is probably the most dramatic example of how time is the magic ingredient in cooking, transforming humble foods into a final dish that is far, far more than the sum of its parts.
With French onion soup, the lengthy cooking time has two phases: Caramelizing the onions slowly and deliberately, and then simmering the broth for a long time with the caramelized onions. Skimping on either side will yield something a little less than the French onion soup of your dreams, but fortunately most of the time is hands-off. You can even do the simmer in a low oven (250°F) or in a slow cooker
My favorite pan for French onion soup: A 6-quart deep sauté pan from Le Creuset.
The Best Pot for French Onion Soup
You've probably seen a hundred photos of French onion soup served forth from a rustic French country crock, tall and fat-bellied. But that's not the pot it was cooked in, I can almost guarantee you. The best pot for making French onion soup is one that is even wider than it is deep, with plenty of surface area to help the onions caramelize and broth to evaporate and concentrate.
My favorite pan for this task is a deep 6-quart Le Creuset sauté pan, but a wide Dutch oven or stockpot would also do well.
A few ways to flavor French onion soup: Cinnamon, star anise, chili peppers, rosemary, thyme, bay leaves.
Simple Is Beautiful (But Herbs Are OK Too)
The beauty of French onion soup is how incredible it tastes even though there are only a few ingredients: onions, salt, pepper, fat, and broth. It doesn't need anything more.
But you may be tempted to give it a few personal tweaks; I fully support this. I love adding a whole star anise, a bay leaf or two, or a sprig of rosemary. But these aren't necessary; just like the optional wine and Julia Child's own suggested finishing splash of brandy, they are fully at the discretion of the cook.
On Cheese & Toast
The cheesy toast, however, is what we all love and desire on our French onion soup — the finishing touch! Leave it off at your peril; your dinner companions may send you back to the kitchen to put it on!
I do, though, have opinions on the cheese and toast served on top of French onion soup. The point, in my world (and in Julia Child's recipe, which this tutorial is based on) is for the cheese to melt into the soup, making it heartier and more satisfying. The point is not for the cheese to congeal on top of the soup, like pizza toppings. You want finely grated cheese, much of which will disappear into the soup, only to be found in long, melting strands by your spoon.
The toast, likewise, shouldn't cover the soup, but be a welcome toasty garnish, soaking up the soup and breaking into bites you can actually fit on your spoon.
Now I may be in the minority here; most of The Kitchn editorial staff is firmly on Team Cheese Lid, which is totally fine! If you want a thick, relatively unmelted lid of cheese, grate your cheese very roughly and and add additional layers during the baking process.
But do try it like this, too. There's quite a lot of cheese in the soup pictured; it just has melted into every delicious bite. Bon appetit!
Ingredients for classic French onion soup.
How To Make French Onion Soup
Makes 6 to 8 one-cup servings. Based on and adapted from Julia Child's Soupe à l'Oignon from Mastering the Art of French Cooking.
What You Need
2 1/2 pounds yellow onions
3 tablespoons unsalted butter
2 tablespoons olive oil
1 teaspoon salt, plus more to taste
Freshly ground black pepper
1/2 teaspoon sugar
8 cups beef, chicken, or vegetable broth
3 tablespoons flour
1/2 cup white wine, optional
1/4 cup brandy, optional
6 to 8 baguette slices, toasted
1 1/2 to 3 cups shredded Gruyere or Parmesan cheese (1/4 to 1/2 cup per serving)
Minced raw shallot or onion, to garnish
Chef's knife and cutting board
4-quart or larger heavy pan, such as a deep sauté pan or Dutch oven
Oven-safe bowls or mugs, optional
Baking sheet or dish
Cut each onion top to bottom: Peel away the skin.
Slice into half moons: Slice each half of the onion into thin, evenly-sized half moons.
Cut the half moon slices in half: You will have at least 6 cups of chopped onions. But don't worry too much about quantities with this recipe; if you have an extra onion to use up, throw it in!
Melt the butter with the oil: Melt the butter in the pan set over medium-low heat.
Add the onions: After the butter foams up and then settles down, add the onions and stir to coat with the butter.
Cover and cook for 15 minutes: Cover the pan and cook for 15 minutes on low heat.
Season the onions: Remove the lid. The onions should have wilted down somewhat. Stir in 1 teaspoon salt, a generous quantity of black pepper, and 1/2 teaspoon sugar (this helps the onions caramelize).
Cook the onions for 40 minutes to 1 hour: Turn the heat up to medium and cook, uncovered and stirring every few minutes, until the onions are deeply browned. Turn down the heat if the onions scorch or stick to the pan; the browning doesn't come through burning, but through slow, even caramelization.
Heat the broth: As the onions approach a deep walnut color, heat the broth in a separate pot.
Add the flour: Add 3 tablespoons flour to the caramelized onions and cook and stir for about 1 minute.
Add broth and simmer for at least 1 hour: Add the hot broth to the caramelized onions and bring to a boil. If using wine, add this now too. Lower the heat and partially cover the pan. (If you want to add other aromatics such as herbs or spices, do so now.) Cook gently over low heat for at least 1 hour or until the broth is slightly reduced.
Taste and season: Taste and season with additional salt and pepper if needed. Add a finishing splash of brandy, if desired!
Top with toast and cheese: Heat the oven to 350°F. Divide the soup between small but deep oven-safe bowls. Top each with a slice (or two) of toasted baguette and sprinkle grated cheese in a thick layer over the bread and up to the edge of the bowl.
Bake for 20 to 30 minutes: Place the bowls on a baking sheet or in a casserole dish. Bake until the cheese is thoroughly melted.
Broil until the cheese is browned: Turn the oven from bake to broil and broil the soup for 1 to 3 minutes or until the cheese is browned and bubbling. Remove carefully from the oven and let cool for a few minutes before serving on heatproof dishes or trivets. Serve with freshly ground pepper and minced fresh onion or shallot, which provides a welcome bite in contrast to the very sweet and mellow soup.
Flour Optional: The flour added to the onions gives the soup a little bit of thickness and body, just enough to nudge it beyond broth-with-onions. But it's optional; if you want to keep it gluten-free just omit the flour.
Raw Onion Garnish: The raw onion or shallot garnish is a really great part of this recipe, in my opinion. It's a classic garnish for French onion soup and it balances the sweet soup with a bit of bite and crunch. Try it!
Recipe originally published September 2010 and updated January 21, 2015.
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(Image credits: Faith Durand)