Ingredients:

  • 4 large longhorn onions, thinly sliced
  • 2 tablespoons unsalted butter
  • 1 tablespoon olive oil
  • 4 cups beef or vegetable stock
  • 1 cup dry white wine (optional, can substitute with additional broth)
  • 1 teaspoon salt
  • ½ teaspoon black pepper
  • 1 tablespoon fresh thyme leaves (or 1 teaspoon dried thyme)
  • 4 slices of crusty French baguette
  • 1 cup grated Gruyère cheese (or Swiss cheese)
  • ½ cup grated Parmesan cheese

Instructions:

  1. Slice longhorn onions thinly, preferably using a mandoline for evenness.
  2. In a large pot, melt butter and olive oil over medium heat. Add sliced onions, sprinkle with salt, and cook slowly until golden brown, about 30 minutes.
  3. Once onions are caramelized, add white wine (if using) and scrape bottom of pot. Pour in stock and add thyme, pepper. Bring to a simmer and let cook for 10 minutes.
  4. Preheat the oven to 400°F (200°C). Toast baguette slices lightly in the oven for about 5 minutes.
  5. Ladle soup into oven-safe bowls. Place toasted baguette on top and sprinkle with Gruyère and Parmesan cheese. Broil until cheese is bubbly and golden, about 3-5 minutes.
  6. Carefully remove from oven, let cool slightly, and enjoy.