Ingredients:

  • 3 lbs Yellow Onions, thinly sliced
  • 1 large Red Onion, thinly sliced
  • 3 Shallots, minced
  • 4 tbsp Unsalted Butter
  • 1 tbsp Extra Virgin Olive Oil
  • 1 tsp Granulated Sugar
  • 1 tsp Kosher Salt
  • 6 cups High-Quality Beef Stock
  • 1/2 cup Dry Sherry or a crisp Dry White Wine
  • 1 tbsp Balsamic Vinegar
  • 1 tsp Fish Sauce
  • 2 sprigs Fresh Thyme
  • 1 Dried Bay Leaf
  • 1 French Baguette, cut into 1-inch thick slices
  • 2 cups Gruyère Cheese, freshly grated
  • 1/2 cup Parmigiano-Reggiano, finely grated
  • 1 clove Garlic, peeled

Instructions:

  1. In a large heavy-bottomed Dutch oven, melt the butter and olive oil over medium-low heat. Add the yellow onions, red onions, shallots, sugar, and salt.
  2. Caramelize the onions slowly for 45 minutes, stirring occasionally, until they reach a deep mahogany color and jammy consistency.
  3. Deglaze the pot with the dry sherry, scraping up all the brown bits (fond) from the bottom. Simmer until the liquid has almost completely evaporated.
  4. Add the beef stock, balsamic vinegar, fish sauce, thyme sprigs, and bay leaf. Bring to a boil, then reduce heat and simmer uncovered for 20 minutes.
  5. While soup simmers, preheat oven to 400°F (200°C). Arrange baguette slices on a baking sheet and toast until dry and lightly golden on both sides. Remove and rub each slice with the raw garlic clove.
  6. Discard the thyme and bay leaf. Ladle soup into oven-safe crocks. Place two toasted baguette slices on top of each, then generously cover with the Gruyère and Parmigiano-Reggiano mixture.
  7. Broil for 3-5 minutes until the cheese is bubbling and browned. Let stand for 5 minutes before serving.