French Onion Soup

A classic French onion soup from Cook’s Illustrated, built around deeply caramelized yellow onions, dry sherry, chicken and beef broths, and fresh thyme. The finished soup is topped with crisp baguette slices and plenty of Gruyère, then broiled until melted, bubbling and beautifully browned.

French Onion Soup

Servings: 6
Prep Time: About 30 minutes
Cook Time: About 4 hours

Ingredients:

For the Soup:

• 3 tablespoons unsalted butter, cut into 3 pieces
• 6 large yellow onions (about 4 pounds), halved and cut pole-to-pole into ¼-inch-thick slices
• Table salt
• 2 cups water, plus additional water for deglazing
• ½ cup dry sherry
• 4 cups low-sodium chicken broth
• 2 cups beef broth
• 6 sprigs fresh thyme, tied together with kitchen twine
• 1 bay leaf
• Freshly ground black pepper

For the Cheese Croutons:

• 1 small baguette, cut into ½-inch slices
• 8 ounces Gruyère cheese, shredded (about 2½ cups)

Instructions:

1. Adjust an oven rack to the lower-middle position and preheat the oven to 400°F. Generously coat the inside of a large, heavy-bottomed Dutch oven of at least 7 quarts with nonstick cooking spray.
2. Add the butter, onions and 1 teaspoon salt to the pot. Cover and cook in the oven for 1 hour.
3. Remove the pot from the oven and stir the onions, scraping the bottom and sides. Return the pot to the oven with the lid slightly ajar and cook until the onions are very soft and golden brown, another 1½–1¾ hours. After the first hour, stir the onions and scrape the bottom and sides of the pot.
4. Carefully transfer the Dutch oven to the stovetop over medium-high heat. Cook the onions, stirring frequently and scraping the bottom and sides, until the liquid evaporates and the onions brown, about 15–20 minutes. Reduce the heat to medium if necessary to prevent burning.
5. Continue cooking and stirring until a dark brown crust develops on the bottom of the pot, about 6–8 minutes.
6. Add ¼ cup water and scrape the bottom thoroughly to loosen the browned fond. Continue cooking until the water evaporates and another dark crust develops, about 6–8 minutes.
7. Repeat this deglazing process 2 or 3 more times, using ¼ cup water each time, until the onions are very dark brown and deeply caramelized.
8. Add the sherry and cook, stirring frequently and scraping the pot, until the sherry has evaporated, about 5 minutes.
9. Stir in the chicken broth, beef broth, 2 cups water, thyme, bay leaf and ½ teaspoon salt, scraping up any remaining browned bits.
10. Increase the heat to high and bring the soup to a simmer. Reduce the heat to low, cover and simmer for 30 minutes.
11. Remove and discard the thyme and bay leaf. Taste and season with additional salt and freshly ground black pepper as needed.
12. While the soup simmers, arrange the baguette slices in a single layer on a baking sheet. Bake at 400°F for about 10 minutes, until dry, crisp and golden around the edges.
13. To serve, position an oven rack about 4–5 inches below the broiler and preheat the broiler.
14. Place individual broiler-safe soup crocks on a baking sheet. Fill each with about 1¾ cups soup.
15. Top each crock with 1 or 2 toasted baguette slices without overlapping them. Generously sprinkle with shredded Gruyère.
16. Broil for 3–5 minutes, until the cheese is completely melted, bubbling and nicely browned.
17. Allow the soup to cool for about 5 minutes before serving.

Tip: Don't rush the onions. The repeated browning and deglazing on the stovetop after their long oven cooking develops the deep caramelized flavor that distinguishes this soup. It is also an excellent make-ahead recipe—the soup can be prepared 1–2 days in advance, then reheated and topped with the bread and Gruyère just before serving.

Source: Cook’s Illustrated, January 1, 2008