Ingredients:

  • 2 tablespoons (30ml) olive oil
  • 4 tablespoons (56g) unsalted butter
  • 3 large yellow onions, thinly sliced (approximately 3 pounds or 1.4kg)
  • 1 teaspoon granulated sugar
  • 1/2 teaspoon kosher salt, plus more to taste
  • 1/4 teaspoon freshly ground black pepper, plus more to taste
  • 2 cloves garlic, minced
  • 1/2 cup (120ml) dry sherry or dry white wine (such as Sauvignon Blanc)
  • 8 cups (1.9L) beef broth (low sodium preferred)
  • 4 sprigs fresh thyme
  • 1 bay leaf
  • 6 slices baguette, about 1 inch thick
  • 6 ounces (170g) Gruyère cheese, grated

Instructions:

  1. Heat olive oil and butter in a large pot. Add onions, sugar, salt, and pepper. Sauté over medium-low heat, stirring occasionally, until the onions are deeply caramelized (about 45-60 minutes).
  2. Stir in minced garlic and cook for another minute until fragrant.
  3. Pour in sherry (or white wine) and scrape up any browned bits from the bottom of the pot. Let the sherry reduce slightly.
  4. Add beef broth, thyme sprigs, and bay leaf. Bring to a simmer, then reduce heat and simmer for at least 30 minutes to allow the flavors to meld. Remove thyme sprigs and bay leaf before serving.
  5. Lightly toast the baguette slices under the broiler.
  6. Ladle soup into oven-safe bowls. Top each bowl with a baguette slice and a generous amount of Gruyère cheese.
  7. Broil until the cheese is melted and bubbly, watching carefully to prevent burning.
  8. Serve immediately. Be careful, the bowls will be hot!