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French Onion Soup

Deeply caramelized onion soup with a crusty bread crouton and melted Gruyère.

French Onion Soup — finished dish

Soup · One-pot • 1 hr 15 min

Servings:
4 servings

Ingredients

  • 3 tablespoons unsalted butter
  • 1 tablespoon olive oil
  • 3 pounds yellow onions (about 4 large), halved and thinly sliced pole-to-pole
  • Kosher salt
  • 4 cloves garlic, minced
  • 2 teaspoons fresh thyme leaves (from about 6 sprigs), plus more for garnish
  • ½ cup dry sherry or dry white wine
  • 6 cups low-sodium beef broth
  • Freshly ground black pepper
  • 1 bay leaf
  • 4 thick slices crusty bread (country loaf or baguette, cut 1-inch thick), toasted
  • 8 ounces Gruyère cheese, grated (about 2 cups)
  • 2 tablespoons grated Parmesan cheese

Steps

  1. Melt butter with olive oil in a large Dutch oven or heavy-bottomed pot over medium heat. Add the sliced onions and a generous pinch of salt. Stir to coat. Cook, stirring every 5 minutes, until the onions are deeply golden brown and jammy, about 40 to 45 minutes. Reduce heat to medium-low if they start to darken too quickly — the color should be a rich caramel, not burnt.
  2. Add minced garlic and thyme. Cook 1 minute, stirring constantly. Pour in the sherry and scrape up any browned bits from the bottom of the pot. Let the sherry reduce by half, about 1 minute.
  3. Add beef broth, bay leaf, and several grinds of black pepper. Bring to a boil, then reduce heat to low, cover, and simmer 15 minutes to let the flavors meld. Discard the bay leaf. Taste and adjust salt and pepper.
  4. While the soup simmers, position an oven rack 6 inches from the broiler and preheat the broiler. Arrange four oven-safe soup bowls or ramekins on a rimmed baking sheet.
  5. Ladle the soup into the bowls, leaving about ½ inch of room at the top. Float a toasted bread slice on each bowl. Divide the grated Gruyère over the bread, mounding it slightly over the edges. Sprinkle Parmesan on top.
  6. Broil until the cheese is bubbling, melted, and browned in spots, about 3 to 5 minutes. Watch closely — broilers vary. Garnish with fresh thyme and serve immediately. The bowls will be extremely hot.