Ingredients

• INGREDIENTS
• Soup
• 3 tablespoons unsalted butter, cut into 3 pieces
• 6 large yellow onions (about 4 pounds), halved and cut pole to pole into 1/4-inch-thick slices (see illustration below)
• Table salt
• 2 cups water, plus extra for deglazing
• ½ cup dry sherry
• 4 cups low-sodium chicken broth (see note)
• 2 cups beef broth
• 6 sprigs fresh thyme, tied with kitchen twine
• 1 bay leaf
• Ground black pepper
• Cheese Croutons
• 1 small baguette, cut into 1/2-inch slices
• 8 ounces shredded Gruyère cheese (about 2 1/2 cups)

Directions

• BEFORE YOU BEGIN
• Sweet onions, such as Vidalia or Walla Walla, will make this recipe overly sweet. Be patient when caramelizing the onions in step 2; the entire process takes 45 to 60 minutes. Use broiler-safe crocks and keep the rim of the bowls 4 to 5 inches from the heating element to obtain a proper gratinée of melted, bubbly cheese. If using ordinary soup bowls, sprinkle the toasted bread slices with Gruyère and return them to the broiler until the cheese melts, then float them on top of the soup. For the best flavor, make the soup a day or 2 in advance. Alternatively, the onions can be prepared through step 1, cooled in the pot, and refrigerated for up to 3 days before proceeding with the recipe.
• 1
• INSTRUCTIONS
• FOR THE SOUP: Adjust oven rack to lower-middle position and heat oven to 400 degrees. Generously spray inside of heavy-bottomed large (at least 7-quart) Dutch oven with nonstick cooking spray. Place butter in pot and add onions and 1 teaspoon salt. Cook, covered, 1 hour (onions will be moist and slightly reduced in volume). Remove pot from oven and stir onions, scraping bottom and sides of pot. Return pot to oven with lid slightly ajar and continue to cook until onions are very soft and golden brown, 1 1/2 to 1 3/4 hours longer, stirring onions and scraping bottom and sides of pot after 1 hour.
• 2
• Carefully remove pot from oven and place over medium-high heat. Using oven mitts to handle pot, cook onions, stirring frequently and scraping bottom and sides of pot, until liquid evaporates and onions brown, 15 to 20 minutes, reducing heat to medium if onions are browning too quickly. Continue to cook, stirring frequently, until pot bottom is coated with dark crust, 6 to 8 minutes, adjusting heat as necessary. (Scrape any fond that collects on spoon back into onions.) Stir in 1/4 cup water, scraping pot bottom to loosen crust, and cook until water evaporates and pot bottom has formed another dark crust, 6 to 8 minutes. Repeat process of deglazing 2 or 3 more times, until onions are very dark brown. Stir in sherry and cook, stirring frequently, until sherry evaporates, about 5 minutes.
• 3
• Stir in broths, 2 cups water, thyme, bay leaf, and 1/2 teaspoon salt, scraping up any final bits of browned crust on bottom and sides of pot. Increase heat to high and bring to simmer. Reduce heat to low, cover, and simmer 30 minutes. Remove and discard herbs, then season with salt and pepper.
• 4
• FOR THE CROUTONS: While soup simmers, arrange baguette slices in single layer on baking sheet and bake in 400-degree oven until bread is dry, crisp, and golden at edges, about 10 minutes. Set aside.
• 5
• To serve: Adjust oven rack 6 inches from broiler element and heat broiler. Set individual broiler-safe crocks on baking sheet and fill each with about 1 3/4 cups soup. Top each bowl with 1 or 2 baguette slices (do not overlap slices) and sprinkle evenly with Gruyère. Broil until cheese is melted and bubbly around edges, 3 to 5 minutes. Let cool 5 minutes before serving.

Notes

• WHY THIS RECIPE WORKS
• With too many onion soups, digging through a layer of congealed cheese unearths a disappointing broth that just doesn’t taste like onions. The ideal French onion soup combines a satisfying broth redolent of sweet caramelized onions with a slice of toasted baguette and melted cheese. We wanted a foolproof method for achieving extraordinarily deep flavor from the humble onion—the star of this classic soup.The secret to a rich broth was to caramelize the onions fully. The good news is that caramelizing the onions, deglazing the pot, and then repeating this process dozens of times will keep ratcheting up the flavor. The bad news is what a laborious, hands-on process this proved to be. Fortunately, we found that if we first cooked the onions covered in a hot oven for two and a half hours, we only needed to deglaze the onions on the stovetop three or four times. Just one type of onion (yellow) was sufficient, but a combination of three different liquids (water, chicken broth, and beef broth) added maximum flavor. For the topping, we toasted the bread before floating it on the soup to ward off sogginess and added only a modest sprinkling of nutty Gruyère so the broth wasn’t overpowered.

Photos