Ingredients:

  • 3 lbs (1.36 kg) Yellow Onions, thinly sliced
  • 4 tbsp (56g) Unsalted Butter
  • 2 tbsp (30 ml) Olive Oil
  • 1 tsp Granulated Sugar
  • 1/2 tsp Baking Soda
  • 1 tsp Dried Thyme
  • 1 Bay Leaf
  • 1/4 cup (60 ml) Dry Sherry (or dry white wine, such as Sauvignon Blanc)
  • 8 cups (1.9 Liters) Beef Broth
  • 2 cups (473 ml) Chicken Broth
  • 1 tbsp Worcestershire Sauce
  • Salt and freshly ground Black Pepper, to taste
  • 6 thick slices Baguette, about 1-inch thick
  • 2 cloves Garlic, halved
  • 2 tbsp (28g) Unsalted Butter, melted
  • 8 oz (227g) Gruyère Cheese, grated

Instructions:

  1. Melt butter and olive oil in a large pot. Add onions, sugar, and baking soda. Cook over medium-low heat, stirring frequently, until deeply caramelized (about 1 hour 15 min).
  2. Add thyme and bay leaf to the onions. Cook for 1 minute. Deglaze with sherry, scraping up any browned bits from the bottom of the pot. Simmer until the sherry is almost evaporated.
  3. Pour in beef and chicken broths. Add Worcestershire sauce. Bring to a simmer. Season with salt and pepper. Reduce heat and simmer for at least 30 minutes, or up to 1 hour, to allow flavors to meld. Remove the bay leaf before serving.
  4. Brush baguette slices with melted butter, then rub with garlic. Arrange on a baking sheet and toast in the oven until lightly golden (about 5 minutes).
  5. Preheat broiler. Ladle soup into oven-safe bowls or ramekins. Top each bowl with a toasted baguette slice and a generous amount of Gruyère cheese.
  6. Place bowls on a baking sheet and broil until the cheese is melted, bubbly, and golden brown (2-3 minutes). Watch carefully to prevent burning!