Ingredients:

  • 3 tablespoons unsalted butter (45g)
  • 4 large yellow onions, thinly sliced (about 4-5 lbs/2-2.25kg)
  • 2 cloves garlic, minced
  • 1 teaspoon dried thyme
  • 1/2 teaspoon dried bay leaf
  • 1/4 cup dry sherry (optional, but adds depth!) (60ml)
  • 8 cups beef broth (low sodium recommended) (1.9 liters)
  • 1 tablespoon Worcestershire sauce (15ml)
  • Salt and freshly ground black pepper, to taste
  • 6 slices baguette, about 1 inch thick
  • 2 tablespoons olive oil
  • 4 ounces Gruyère cheese, shredded (115g)
  • Optional: A sprinkle of freshly chopped parsley to garnish

Instructions:

  1. Melt butter in a large skillet over medium-low heat. Add sliced onions, thyme, bay leaf and garlic and cook, stirring occasionally, until the onions are deeply caramelized and golden brown (about 30-45 minutes). Stir occasionally to prevent burning.
  2. If using, deglaze the pan with sherry, scraping up any browned bits from the bottom. Cook for 1-2 minutes to evaporate the alcohol.
  3. Transfer caramelized onions and any liquid to the slow cooker.
  4. Pour in beef broth and Worcestershire sauce. Season with salt and pepper to taste.
  5. Cover and cook on low for 6-8 hours, or on high for 3-4 hours.
  6. Preheat oven to 400°F (200°C). Brush baguette slices with olive oil and bake for 5-7 minutes, or until lightly toasted.
  7. Remove bay leaf from the soup. Ladle soup into oven-safe bowls. Top each bowl with a toasted baguette slice and generous amount of shredded Gruyère cheese.
  8. Broil (or grill) in the oven for 2-3 minutes, or until the cheese is melted and bubbly. Watch carefully to prevent burning!
  9. Garnish with fresh parsley (if desired) and serve immediately.