How to Make Classic French Three Onion Soup

French onion soup is a timeless classic but this version takes it up a notch by incorporating not just one, but three types of onions for a more complex, layered flavor. Combining sweet yellow onions, shallots, and leeks, this French Three Onion Soup is slowly caramelized until golden and rich, then simmered in broth and finished with a broiled Gruyere topping for a cozy, elevated dish that satisfies.

Perfect for cool evenings, elegant dinner starters, or even a light main dish with a crisp salad, this soup delivers all the comfort you crave with a sophisticated French twist.

Ingredients

• 1 tablespoon unsalted butter

• 1 teaspoon extra-virgin olive oil

• 1½ pounds yellow onions, peeled, halved, and thinly sliced (about 6 cups)

• 6 shallots, thinly sliced (about 1¾ cups)

• 1 leek, white and light green parts thinly sliced and well-washed; reserve dark green top

• Kosher salt and freshly ground black pepper, to taste

• 3 to 4 fresh thyme sprigs

• 1 fresh rosemary sprig

• 1 tablespoon all-purpose flour

• 4 cups low-sodium beef broth

• 2 cups water

• 2 teaspoons Worcestershire sauce

• ¼ cup dry sherry

• 8 slices whole-wheat baguette, ¼-inch thick (about 2 ounces total), toasted

• ½ cup finely grated Gruyere cheese (about 1¾ ounces)

• 1 tablespoon chopped fresh chives, for garnish

Directions

1. Caramelize the Onions
In a large Dutch oven, heat the butter and olive oil over medium heat. Add the yellow onions, shallots, and leek. Season lightly with salt and pepper. Stir to combine, then cover and let cook without stirring for 10–15 minutes, until softened and just beginning to brown.

Uncover and continue cooking for 25–30 minutes, stirring frequently, until the onions are deeply caramelized and golden brown. If the onions begin to stick or brown too quickly, add a tablespoon of water as needed.

2. Add the Herbs and Flour
Tie the reserved dark green leek top with the thyme and rosemary sprigs using kitchen twine to form a bouquet garni. Sprinkle the flour over the caramelized onions and stir to cook for 2–3 minutes to eliminate the raw flour taste.

3. Simmer the Soup
Pour in the beef broth and water, scraping up any browned bits from the bottom of the pot. Add the herb bundle. Lower the heat and simmer gently for 20–25 minutes, or until the soup is slightly thickened and aromatic. Stir in Worcestershire sauce, remove from heat, discard the herb bundle, and stir in the sherry. Taste and adjust seasoning with salt and pepper.

4. Broil the Bowls
Preheat your broiler. Ladle the soup into 4 ovenproof bowls or ramekins (about 16 ounces each) and place them on a baking sheet. Top each bowl with 2 toasted baguette slices and sprinkle evenly with Gruyere.

Broil for 1–2 minutes, watching closely, until the cheese is melted and bubbling with golden spots. Garnish with chopped chives.

Serving Suggestion

Turn this rich soup into a light, elegant meal by serving it with a side salad of baby mixed greens, sliced endive, and roasted beets tossed in a lemon vinaigrette. The brightness of the salad cuts through the richness of the soup, creating the perfect balance.

The Bottom Line

This French Three Onion Soup is more than a comfort classic it’s a celebration of simple, slow-cooked ingredients coming together in perfect harmony. Whether you’re preparing it for a cozy night in or a dinner party starter, this dish delivers sophistication and heartwarming flavor in every bite.

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