Description
A deeply savory, soul-warming classic French onion soup made with slowly caramelized yellow onions, rich beef broth, and a splash of sherry vinegar for brightness. Finished with toasted baguette slices and a bubbling crown of melted Gruyère and Parmesan cheese, this soup delivers silky onion sweetness balanced by nutty, salty cheese and crusty bread in every spoonful.
Ingredients
- 4 tablespoons unsalted butter, divided into 3 tbsp and 1 tbsp
- 1 1/2 pounds yellow onions (about 5 medium onions), halved through the root and thinly sliced into half-moons, about 6 cups
- 1 teaspoon kosher salt, divided into 1/2 tsp and 1/2 tsp
- 1/2 teaspoon granulated sugar
- 3 tablespoons all-purpose flour
- 6 cups good-quality beef broth, preferably low-sodium
- 1/4 cup dry sherry or 2 tablespoons sherry vinegar plus 2 tablespoons water (for a non-alcoholic option, use 2 tablespoons sherry vinegar and 2 tablespoons water)
- 1 bay leaf
- 2 fresh thyme sprigs or 1/2 teaspoon dried thyme
- 1/2 teaspoon freshly ground black pepper
- 8 slices day-old French baguette, cut 1/2-inch thick on the diagonal
- 1 1/2 cups Gruyère cheese, coarsely grated
- 1/3 cup Parmesan cheese, finely grated
Instructions
- Prepare the onions: Peel the onions, cut each in half through the root end, then place flat side down and slice thinly into half-moons about 1/8-inch thick. You should have roughly 6 cups of sliced onions; set them aside in a large bowl.
- Melt 3 tablespoons of unsalted butter in a large 5- to 6-quart heavy-bottomed Dutch oven or soup pot over medium-low heat. Once the butter has fully melted and the foam subsides, add the sliced onions all at once and stir with a wooden spoon to coat them evenly in the butter.
- Add 1/2 teaspoon kosher salt and 1/2 teaspoon granulated sugar to the onions. The salt draws out moisture to help the onions soften, while the sugar accelerates the browning process and deepens the final color. Stir well to distribute.
- Cook the onions over medium-low heat, uncovered, stirring every 3 to 5 minutes with a flat-edged wooden spatula, for 45 to 55 minutes. The onions will first soften and release liquid, then gradually turn golden, and finally become a deep, rich mahogany brown. If the onions start to scorch or stick too quickly, reduce the heat slightly and add 1 to 2 tablespoons of water to deglaze the bottom of the pot.
- When the onions are deeply caramelized and reduced to about 1 1/2 cups, sprinkle 3 tablespoons of all-purpose flour over them. Stir continuously for 2 to 3 minutes over medium heat so the flour coats the onions and cooks out its raw taste; this will help thicken the soup later.
- Pour in 6 cups of beef broth slowly while stirring constantly to prevent lumps from forming. Scrape the bottom of the pot with your spatula to release any browned bits, which add intense flavor to the soup.
- Add the bay leaf, thyme sprigs, 1/2 teaspoon freshly ground black pepper, and the sherry vinegar mixture (or dry sherry if using). Bring the soup to a gentle simmer over medium heat, then reduce the heat to low and let it simmer, partially covered, for 28 to 30 minutes. The soup should reduce slightly and the flavors will meld and deepen.
- While the soup simmers, preheat the oven to 425°F / 218°C with a rack set in the upper third of the oven. Arrange 8 slices of day-old baguette in a single layer on a rimmed baking sheet. Bake for 5 to 7 minutes until the bread is dry, lightly golden, and crisp at the edges. Set aside.
- Taste the soup and season with the remaining 1/2 teaspoon kosher salt, or adjust to taste with additional salt and black pepper as needed. Remove and discard the bay leaf and thyme stems.
- Ladle the hot soup into 4 oven-safe ramekins or deep soup bowls, filling each about three-quarters full. Place the ramekins or bowls on a rimmed baking sheet to catch any cheese drips during broiling.
- Top each bowl with 2 slices of toasted baguette, laying them flat over the surface of the soup so they float like a raft. Sprinkle each bowl generously with about 1/3 cup of grated Gruyère, letting some cheese fall onto the rim of the bowl. Dust each bowl with about 1 tablespoon of finely grated Parmesan.
- Place the baking sheet with the filled bowls in the oven under the preheated broiler on high heat. Broil for 3 to 5 minutes, rotating the pan halfway through, until the cheese is melted, golden brown, and bubbling at the edges. Watch carefully because the cheese can burn in seconds.
- Carefully remove the baking sheet from the oven and let the bowls rest for 2 minutes before serving. The soup underneath will be scalding hot, so caution diners about the first spoonful. Serve each bowl on a folded napkin or trivet to protect the table.
Notes
Store leftover soup (without the bread and cheese) in an airtight container in the refrigerator for up to 4 days. For freezing, cool the soup completely and freeze in freezer-safe containers for up to 3 months; thaw overnight in the refrigerator. To reheat, warm the soup gently in a saucepan over medium-low heat until simmering, then ladle into oven-safe bowls and top with fresh toasted baguette slices and cheese before broiling as directed. Do not freeze the assembled soup with bread and cheese, as the bread will become mushy and the cheese will lose its texture.
Nutrition
- Calories: 438
- Sugar: 12g
- Sodium: 1580mg
- Unsaturated Fat: 14g
- Carbohydrates: 38g
- Fiber: 4g
- Protein: 20g
- Cholesterol: 68mg
Keywords: Julia Child French onion soup, French onion soup recipe, classic French onion soup, caramelized onion soup, Gruyere onion soup, beef broth onion soup, cozy winter soup, baked French onion soup, vegetarian French onion soup, day old bread soup, stovetop soup recipe, bistro style soup