Ingredients:

  • 5 lbs (2.5 kg) Yellow Onions, peeled, thinly and uniformly sliced
  • 1 Tbsp (15 g) Unsalted Butter
  • 1 Tbsp (15 ml) Extra Virgin Olive Oil
  • 1 tsp (5 g) Fine Sea Salt, plus more for finishing
  • 4 Fresh Thyme Sprigs, tied into a bundle
  • 1 Dried Bay Leaf
  • 1 Tbsp (8 g) All-Purpose Flour
  • 1/3 cup (80 ml) Dry Sherry or Port
  • 5 cups (1.8 L) Low-Sodium Beef Stock
  • 1 tsp Worcestershire Sauce or Soy Sauce (optional)
  • 8 (1-inch/2.5cm) slices Baguette, sliced on the bias
  • 7 oz (200 g) Gruyère Cheese, freshly grated
  • Black Pepper, freshly cracked, to taste

Instructions:

  1. Slice all onions uniformly (about 3mm). Tie the thyme sprigs together tightly with kitchen string (bouquet garni style) and set aside with the bay leaf. Grate the Gruyère and set aside. Preheat the grill/broiler to high.
  2. Heat the butter and olive oil in a Dutch Oven over medium-low heat. Add the sliced onions and the 1 tsp of salt.
  3. Cook the onions, stirring occasionally, for 15 minutes until they have significantly wilted and released most of their moisture.
  4. Reduce the heat to low. Continue cooking, stirring every 5-8 minutes, scraping the bottom constantly. Cook for 45–60 minutes total, until the onions achieve a rich, dark mahogany color without any bitterness. If dark bits (fond) form too quickly, deglaze with a splash of water or stock immediately and scrape them up.
  5. Pour in the sherry or port. Increase the heat to medium and scrape up any remaining brown bits. Cook until the liquid has almost completely evaporated (about 2 minutes).
  6. Sprinkle the flour over the onions (the 'singer' method) and stir well for 1 minute to cook out the raw flour taste.
  7. Pour in the beef stock and add the thyme bundle and bay leaf (and optional umami booster). Bring the mixture to a low simmer. Reduce the heat and let the soup simmer gently, uncovered, for 20 minutes to allow the flavours to marry.
  8. Remove and discard the thyme bundle and bay leaf. Taste the soup and adjust salt and pepper as needed until the soup tastes robustly savoury.
  9. While the soup simmers, lightly toast the baguette slices on a baking sheet until golden and crisp (about 5 minutes). This prevents them from dissolving quickly in the soup.
  10. Ladle the hot soup into four oven-safe ceramic crocks. Place one or two toasted baguette slices on top of the soup in each crock.
  11. Divide the grated Gruyère evenly over the bread slices, ensuring the cheese covers the entire crouton and touches the rim of the crock.
  12. Place the crocks onto a baking tray and slide them under the preheated grill/broiler. Broil for 2–4 minutes until the cheese is bubbling, golden brown, and slightly blistered. Watch constantly to avoid burning. Serve immediately.