Ingredients:

  • 3 tablespoons (45ml) unsalted butter
  • 2 tablespoons (30ml) olive oil
  • 3 pounds (1.36 kg) yellow onions, thinly sliced
  • 1 teaspoon (5ml) granulated sugar
  • 1/2 teaspoon (2.5ml) kosher salt, plus more to taste
  • 1/4 teaspoon (1.25ml) black pepper, plus more to taste
  • 1/4 cup (60ml) dry sherry or dry white wine (optional)
  • 8 cups (1.9 liters) beef broth or stock
  • 2 sprigs fresh thyme
  • 1 bay leaf
  • 1 tablespoon (15ml) Worcestershire sauce
  • 6 slices baguette, about 1 inch (2.5cm) thick
  • 2 tablespoons (30ml) olive oil, for brushing
  • 6 ounces (170g) Gruyère cheese, shredded (or a mix of Gruyère and Swiss)

Instructions:

  1. Melt butter and olive oil in a large pot over medium-low heat. Add onions, sugar, salt, and pepper. Cook, stirring occasionally, until the onions are deeply caramelized and a rich golden-brown color (this will take 1-1.5 hours).
  2. If using, pour in the sherry or white wine and scrape up any browned bits from the bottom of the pot. Cook until the liquid has almost completely evaporated.
  3. Pour in the beef broth/stock, add thyme, bay leaf, and Worcestershire sauce. Bring to a simmer, then reduce heat to low and simmer for at least 30 minutes to allow the flavors to meld. Season to taste with salt and pepper.
  4. Preheat oven to 400°F (200°C). Brush baguette slices with olive oil and bake on a baking sheet for 5-7 minutes, or until lightly toasted.
  5. Preheat broiler. Ladle soup into oven-safe bowls. Top each bowl with a toasted baguette slice and a generous amount of shredded Gruyère cheese.
  6. Place the bowls under the broiler for 2-3 minutes, or until the cheese is melted, bubbly, and golden brown. Watch carefully to prevent burning!
  7. Let cool slightly before serving.