Ingredients:

  • 5 large yellow onions, thinly sliced (approx. 3 lbs / 1.35kg)
  • 4 tbsp unsalted butter (57g)
  • 2 tbsp olive oil (30ml)
  • 1 tsp granulated sugar (5g)
  • 1 tsp kosher salt (6g)
  • 1/2 tsp black pepper (1g)
  • 6 cups beef broth (1.4L)
  • 1/2 cup dry white wine (120ml)
  • 3 cloves garlic, minced (15g)
  • 2 sprigs fresh thyme (2g)
  • 1 bay leaf
  • 1 baguette, sliced into 1-inch rounds (approx. 12 oz / 340g)
  • 2 cups Gruyère cheese, grated (225g)
  • 1/4 cup Parmesan cheese, grated (25g)

Instructions:

  1. Melt the butter and olive oil in a Dutch oven over medium heat. Add the sliced onions and toss to coat, cooking for 10–15 minutes until translucent and soft.
  2. Stir in the sugar, salt, and pepper. Reduce heat to medium-low and cook the onions for 45–60 minutes, stirring every 10 minutes, until they reach a deep mahogany color. Add a tablespoon of water if onions stick too much.
  3. Add minced garlic and cook for 1 minute until fragrant. Pour in the white wine to deglaze the pot, scraping the bottom thoroughly.
  4. Stir in the beef broth, thyme, and bay leaf. Simmer on low for 20 minutes. Remove the thyme sprigs and bay leaf before serving.
  5. Toast baguette slices on a baking sheet until crisp.
  6. Ladle the soup into oven-safe crocks. Top each serving with a toasted baguette slice and a generous portion of Gruyère and Parmesan cheese.
  7. Place crocks under the broiler until the cheese is melted and bubbling brown.