Ingredients:

  • 3 lbs (1.36 kg) yellow onions, thinly sliced
  • 4 tbsp (57g) unsalted butter
  • 2 tbsp (30ml) olive oil
  • 1 tsp granulated sugar
  • 1/2 tsp dried thyme
  • 1/4 tsp dried bay leaf
  • 1/2 cup (120ml) dry sherry or dry white wine
  • 8 cups (1.9 liters) beef broth (low sodium preferred)
  • Salt and freshly ground black pepper to taste
  • 1 baguette, sliced into 1-inch thick rounds
  • 4 tbsp (57g) unsalted butter, melted
  • 6 oz (170g) Gruyère cheese, shredded

Instructions:

  1. Melt butter and olive oil in a large pot. Add onions, sugar, thyme, bay leaf, salt and pepper. Cook over medium-low heat, stirring occasionally, until onions are deeply caramelized and golden brown (about 45-60 minutes).
  2. Pour in sherry or white wine and scrape up any browned bits from the bottom of the pot. Cook until the liquid is almost completely evaporated.
  3. Add beef broth and bring to a simmer. Reduce heat and simmer for at least 30 minutes to allow the flavors to meld. Adjust seasoning to taste. Remove bay leaf before serving.
  4. Preheat oven to 375°F (190°C). Brush baguette slices with melted butter and arrange on a baking sheet. Bake until golden brown and crispy (about 8-10 minutes).
  5. Preheat broiler. Ladle soup into oven-safe bowls. Top each bowl with several croutons and a generous amount of Gruyère cheese. Broil until the cheese is melted, bubbly, and lightly browned (about 2-3 minutes).
  6. Let cool slightly before serving.