Traditional French Onion Soup


Preparation info

  • Difficulty


  • Serves

    4 to 6

Appears in

Ruhlman's Twenty

By Michael Ruhlman

Published 2011

  • About

The power of water joins the power of onion in what may be one of the best soups in the Western canon. The soup deserves this high praise not only because it’s delicious and satisfying, but because it was borne out of economy. This is a peasant soup, made from onions, a scrap of old bread, some grated cheese, and water. Season with salt and whatever wine is on hand or some vinegar. Do not be tempted to use stock! Even if it’s really good homemade stock, it will detract from the economy of the dish, which can easily become too heavy and cloying. (And please don’t add the canned stuff. How many onion soups have been trashed by adding store-bought broth? A fair share in my kitchen until I learned how to use water.)

I’ve never seen a recipe for onion soup that didn’t use stock or broth, and yet this changes the soup completely—it becomes beef-onion soup or chicken-onion soup. I could not find a historical basis for my conviction until I began researching a specific style of bistro in Lyon, France, called a bouchon (boo-SHOHN). There are only about twenty of these restaurants in Lyon, and they serve a very distinct, country-style, family-meal menu. At some, you sit at communal tables, and platters are passed from table to table. What I like about bouchons is that they serve elemental, efficient food. It had to be, as a husband and wife usually worked the place. I spoke with a journalist in Lyon, an expert on the subject of la vrai bouchon, “the true bouchon,” who confirmed what I’d always suspected. At a bouchon, and indeed at most peasant households, a time-consuming and costly stock would not be used for onion soup. Onions and a splash of wine for seasoning and a crust of bread with some cheese melted on it— that is all you need to make a very fine soup with a pure caramelized onion flavor.

Plan ahead when making the soup because the onions take a long time to cook down, from a few hours to as many as five if you keep the heat very low, though you need to pay attention only at the beginning and the end. Before the onions caramelize, they’ll release copious amounts of water (be sure to taste this liquid!), which must cook off first. You can simmer the onions hard if you want to reduce the cooking time; be sure to tend the pot and stir often, or the onions can stick and burn. You can also caramelize the onions a day or two in advance, and refrigerate them until needed. If you do this, the final soup can be finished in the time it takes to heat the water and melt the cheese on top.


  • 1 tablespoon butter
  • 7 or 8 Spanish onions (7 to 8 pounds/3.2 to 3.6 kilograms), thinly sliced
  • Kosher salt
  • Freshly ground black pepper
  • 6 to 12 slices of baguette or any country-style bread (it’s best if they cover the width of your serving bowls)
  • cup/75 milliliters sherry
  • Red or white wine vinegar (optional)
  • Red wine (optional)
  • ½ to ¾ pound/225 to 340 grams gruyère or emmenthaler cheese, grated


Use a large pot, with a capacity of about quarts/7.1 liters, that will hold all the onions. An enameled cast-iron pot will provide the best surface. Place the pot over medium heat and melt the butter. Add the onions, sprinkle with 2 teaspoons salt, cover, and cook until the onions have heated through and started to steam. Uncover, reduce the heat to low, and cook, stirring occasionally (you should be able to leave the onions alone for an hour at a stretch once they’ve released their water). Season with several grinds of pepper.

Preheat the oven to 200°F/95°C. Place the bread slices in the oven and let dry completely (you can leave the slices in the oven indefinitely, as the heat is not high enough to burn them).

When the onions have completely cooked down, the water has cooked off, and the onions have turned amber—this will take several hours— add 6 cups/1.4 liters of water. Raise the heat to high and bring the soup to a simmer, then reduce the heat to low. Add the sherry. Taste and season with salt and pepper as needed. If the soup is too sweet, add some vinegar. If you would like a little more depth, add a splash of red wine. I like the onion-to-liquid ratio with 6 cups of water. But if you’d prefer a little more delicate soup, add 1 cup/240 milliliters water.

Preheat the broiler/grill. Portion the soup into ovenproof bowls, float the bread on top, cover with the cheese, and broil/grill until the cheese is melted and nicely browned. Serve immediately.

  1. Properly browned onions should be uniformly brown.

  2. Once your onions are brown, add water to extract the flavor.

  3. Cheese will cover the bowls uniformly if grated, not sliced.

  4. Ladle hot soup into bowls before covering with bread and cheese.

  5. Onion soup should be so thick with onions that the croutons rest on top.

  6. Serving in small bowls covered with cheese makes for a nice presentation.