Classic French Onion Soup Recipe
Why This French Onion Soup Recipe Works:
With too many onion soups, digging through a layer of congealed cheese unearths a disappointing broth that just doesn’t taste like onions. The ideal French onion soup recipe combines a satisfying broth redolent of sweet caramelized onions with a slice of toasted baguette and melted cheese. We wanted a foolproof method for achieving extraordinarily deep flavor from the humble onion—the star of this classic soup.
The secret to a rich broth was to caramelize the onions fully. The good news is that caramelizing the onions, deglazing the pot, and then repeating this process dozens of times will keep ratcheting up the flavor. The bad news is what a laborious, hands-on process this proved to be. Fortunately, we found that if we first cooked the onions, covered, in a hot oven for two and a half hours, we only needed to deglaze the onions on the stovetop three or four times. Just one type of onion (yellow) was sufficient, but a combination of three different liquids (water, chicken broth, and beef broth) added maximum flavor. For the topping, we toasted the bread before floating it on the soup to ward off sogginess and added only a modest sprinkling of nutty Gruyère so the broth wasn’t overpowered.
Sweet onions, such as Vidalia or Walla Walla, will make this dish overly sweet. Be patient when caramelizing the onions in step 2; the entire process takes 45 to 60 minutes. Use broiler-safe crocks and keep the rims of the bowls 4 to 5 inches from the heating element to obtain a proper gratinée of melted, bubbly cheese. If using ordinary soup bowls, sprinkle the toasted bread slices with Gruyère and return them to the broiler until the cheese melts, then float them on top of the soup. For the best flavor, make the soup a day or two in advance. Alternatively, the onions can be prepared through step 1, cooled in the pot, and refrigerated for up to 3 days before proceeding with the recipe.
- 3tablespoons unsalted butter, cut into 3 pieces
- 4pounds onions (about 6 large), halved pole to pole and sliced lengthwise ¼ inch thick (see note)
- Table salt
- 2cups water, plus extra for deglazing
- ½cup dry sherry
- 4cups low-sodium chicken broth
- 2cups beef broth
- 6sprigs fresh thyme, tied together with kitchen twine
- 1bay leaf
- Ground black pepper
- 1small baguette, cut on the bias into ½-inch slices
- 8ounces Gruyère cheese, shredded (about 2 cups)
- For the soup:Adjust an oven rack to the lower-middle position and heat the oven to 400 degrees. Generously spray the inside of a large (at least 7-quart) Dutch oven with vegetable oil spray. Add the butter, onions, and 1 teaspoon salt to the pot. Cook, covered, for 1 hour (the onions will be moist and slightly reduced in volume). Remove the pot from the oven and stir the onions, scraping the bottom and sides of the pot. Return the pot to the oven with the lid slightly ajar and continue to cook until the onions are very soft and golden brown, 1½ to 1¾ hours longer, stirring the onions and scraping the bottom and sides of the pot after 1 hour.
- Carefully remove the pot from the oven and place over medium-high heat. Cook the onions, stirring frequently and scraping the bottom and sides of the pot, until the liquid evaporates and the onionsbrown, 15 to 20 minutes, reducing the heat to medium if the onions are browning too quickly. Continue to cook, stirring frequently, until the pot bottom is coated with a dark crust, 6 to 8 minutes, adjusting the heat as necessary. (Scrape any browned bits that collect on the spoon back into the onions.) Stir in ¼ cup water, scraping the pot bottom to loosen the crust, and cook until the water evaporates and the pot bottom has formed another dark crust, 6 to 8 minutes. Repeat the process of deglazing 2 to 3 more times, until the onions are very dark brown. Stir in the sherry and cook, stirring frequently, until the sherry evaporates, about 5 minutes.
- Stir in 2 cups water, the chicken broth, beef broth, thyme, bay leaf, and ½ teaspoon salt, scraping up any final bits of browned crust on the bottom and sides of the pot. Increase the heat to high and bring to a simmer. Reduce the heat to low, cover, and simmer for 30 minutes. Remove and discard the thyme and bay leaf, then season with salt and pepper to taste.
- For the croutons:While the soup simmers, heat the oven to 400 degrees. Arrange the baguette slices in a single layer on a rimmed baking sheet and bake until dry, crisp, and golden at the edges, about 10 minutes. Set aside.
- Adjust an oven rack 6 inches from the broiler element and heat the broiler. Set individual broiler-safe crocks on the baking sheet and fill each with about 1¾ cups of the soup. Top each bowl with one or two baguette slices (do not overlap the slices) and sprinkle evenly with the Gruyère. Broil until the cheese is melted and bubbly around the edges, 3 to 5 minutes. Cool for 5 minutes; serve.