This soup is pure umami flavor at its finest, and it’s probably the most popular soup at Beast. Rich and salty, hearty and cheesy, when French onion soup is done correctly, the flavors are perfectly balanced. The star here is the onion, showcased at its deeply caramelized peak. (I always use yellow onions for caramelizing; sweet onions taste great but contain too much water to brown well.)
I love to make French onion soup with some of the leftover liquid from making a braise, such as Balsamic Braised Short Ribs. Braising liquid has a lovely meaty richness and acidity from the wine that complements the stock and onions; it does increase the salt level, so be aware of that when seasoning this soup. You can replace up to 2 cups of the stock with leftover braising liquid from another recipe.
Making this soup takes a bit of effort. You should make the stock, which takes two (mostly passive) days to prepare. And deeply caramelizing onions takes time, as well. For this reason, I don’t recommend halving this recipe, even if you don’t plan to eat all of it at once. The soup freezes well, so make a big batch and save some for later. You’ll be glad you did.
- Yield: 6 to 8 Servings
- 2 tablespoons extra-virgin olive oil
- 8 large yellow onions, quartered lengthwise and sliced into half-
- moons ⅛ inch thick
- 2½ teaspoons salt
- ¼ cup dry sherry
- 2 teaspoons 30-year aged balsamic vinegar
- 2½ quarts homemade stock or other high-quality stock
- ¼ teaspoon fish sauce
- 0.125 teaspoon Tabasco sauce
- Freshly ground black pepper
- 6 to 8 baguette slices, each ¼ inch thick
- 2 tablespoons butter, melted
- 1 clove garlic
- 1¼ pounds Gruyère cheese, grated
- In an 8- to 10-quart heavy pot or Dutch oven, heat the oil over medium heat. (I don’t like to caramelize onions in butter because they lose their translucent sheen when they cool.) Add the onions and 1¼ teaspoons of the salt and stir often until the onions begin to turn translucent and become very soft, almost soupy, 20 to 25 minutes. (If the largest pot you own holds only 4 to 6 quarts, don’t despair! Simply cook about two-thirds of the onions first, and when they have sweated down and lost much of their volume, add the last third of the onions to the pan and continue cooking. Caramelizing the onions in stages will, of course, increase your cooking time slightly.)
- Turn the heat to just below medium and stir only occasionally, allowing the onions to develop a fond, or crust, on the bottom of the pan. Every few minutes, scrape off the fond and stir it into the onions, then spread the onions evenly across the pan and allow a fond to form again. You want the fond to exist but not to get so dark that it cannot be fully blended back into the onions, leaving you with little black flecks. The onions should take on a lovely amber hue, but don’t let them get too dark. Stir more frequently at the end of caramelizing to ensure they don’t burn. The onions should be a deep caramel hue after 25 to 35 minutes.
- Continue cooking the onions and scraping often. After about 45 minutes, add the sherry and balsamic vinegar and allow them to cook down. After about 1 hour, the onions should be just about done. When finished, they should be a deep caramel brown that is nearly the same color as the broth, not a blond “wood” shade (see photo). Taste for salt and add the remaining 1¼ teaspoons of salt if necessary (the onions should be well seasoned); if you’ll be using braising liquid, season with less salt.
- Add the stock to the pot and turn down the heat to low. Gently simmer the stock and onions for 15 to 20 minutes, until the flavors have melded. Add the fish sauce and Tabasco, a few turns of the pepper mill, and adjust for salt as needed.
- Preheat the oven to 350°F. Lay the baguette slices on a baking sheet and brush one side of each slice with the melted butter. Toast in the oven until light golden brown, 5 to 7 minutes. Remove the toasts, rub lightly with the garlic clove, and turn the oven to broil.
- Arrange broiler-proof bowls on a baking sheet and ladle the soup into the bowls, filling them nearly to the top. Float 1 baguette slice on top of each bowl. Sprinkle the Gruyère on top of the baguette slices, dividing it evenly. It will seem like a giant mountain of cheese, but if you use any less, it won’t form a delicious crust over the top. Place the bowls under the broiler for
- 5 to 7 minutes, until the cheese is browned and bubbly. Serve immediately and be sure to warn guests that the liquid is very hot.