French Onion Soup with Gruyère Croûte

Ingredients

• 3 lbs yellow onions (about 6 medium), thinly sliced
• 4 tbsp unsalted butter
• 2 tbsp olive oil
• 1 tsp sugar
• 1/2 cup dry sherry or dry white wine
• 4 cups beef broth
• 2 cups chicken broth
• 1 tbsp Worcestershire sauce
• 2 sprigs fresh thyme
• 1 bay leaf
• 8 thick slices of baguette, toasted
• 2 cups Gruyère cheese, grated
• 1/4 cup Parmigiano-Reggiano, grated
• Salt and black pepper to taste

Instructions

1. 1

   Melt butter with olive oil in a large, heavy Dutch oven over medium heat. Add all the onions and stir to coat. Season with salt.

2. 2

   Cook onions, stirring every 5–10 minutes, for 45–60 minutes over medium to medium-low heat until they are a deep amber-brown. Add the sugar halfway through to accelerate caramelization. Do not rush this step.

3. 3

   Pour in sherry and scrape up all the browned bits from the bottom of the pot. Cook until the wine has fully evaporated.

4. 4

   Add beef broth, chicken broth, Worcestershire sauce, thyme, and bay leaf. Season with pepper. Bring to a boil, then reduce heat and simmer uncovered for 20 minutes.

5. 5

   Discard thyme sprigs and bay leaf. Taste and adjust seasoning.

6. 6

   Preheat the oven broiler to high. Set oven-safe soup crocks or ramekins on a baking sheet.

7. 7

   Ladle soup into crocks. Place 1–2 toasted baguette slices on top of each soup, pressing them down slightly.

8. 8

   Generously top with Gruyère and a sprinkle of Parmigiano. Broil for 3–5 minutes until the cheese is melted, bubbly, and spotted with dark golden patches.

9. 9

   Serve immediately. Warn guests — the crocks will be very hot.