Classic French Onion Soup (Soupe à l'Oignon Gratinée)

French Onion Soup is a timeless dish that embodies the rich, caramelized sweetness of onions balanced by the savory depth of broth and the indulgent melt of Gruyère cheese. Originating in France, this comforting soup has been a staple in bistros and home kitchens alike, offering a perfect blend of rustic simplicity and refined flavor. The slow-cooked onions develop a deep, complex taste, while the toasted bread and bubbling cheese create a satisfying contrast in texture. Whether enjoyed as a starter or a hearty meal, this dish is a celebration of patience and technique, rewarding the cook with layers of umami and warmth in every spoonful.

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Ingredients (Makes 4 servings)

Ingredients

6 tablespoons (90g) unsalted butter, plus more for bread
3 pounds (1.4kg) yellow or mixed onions, sliced ⅛ inch thick
Kosher salt and freshly ground black pepper, to taste
½ cup (120ml) dry sherry (such as Amontillado)
2 quarts (1.8L) homemade or store-bought low-sodium chicken stock
2 sprigs thyme
1 bay leaf
1 teaspoon (5ml) Asian fish sauce (optional)
1 teaspoon (5ml) cider vinegar
8 bowl-size slices rustic bread, toasted until crisp
1 medium clove garlic
1 pound (450g) Gruyère cheese, grated

For Serving/Garnishing

Freshly minced chives

Nutrition Information (per 100g)

Calories: 120
Fat: 7
Protein: 5
Carbohydrates: 10
Fiber: 1

Directions

Caramelizing the Onions

1. In a large stainless steel saucepan or two large stainless steel or cast iron skillets, melt butter over medium-high heat until foaming. Add onions and cook, stirring occasionally, until softened, about 8 minutes.

2. Reduce heat to medium-low and continue cooking, stirring frequently, until onions are deeply caramelized and golden-brown, 1 to 2 hours. If browned onion juices on the bottom of the pot threaten to burn, add 1 tablespoon (15ml) water, scrape up browned bits, and continue cooking. Season with salt and pepper.
4. Cook until the alcohol smell dissipates, about 3 minutes. Add stock, thyme, and bay leaf. Raise heat to medium-high and bring to a simmer, then reduce heat and let simmer for 20 minutes.
5. Add fish sauce, if using, and cider vinegar. Season with salt and pepper. Remove and discard thyme sprigs and bay leaf.
8. Sprinkle some grated cheese over the bread, then ladle more soup and onions on top, nearly filling the bowls.
9. Place the remaining toasted bread slices in the bowls, pressing them down slightly. Top with the remaining grated cheese.
10. Set the bowls on a rimmed baking sheet and broil until the cheese is melted and browned in spots.
11. Garnish with freshly minced chives and serve immediately.

Building the Soup Base

3. Add sherry and bring to a simmer, scraping up any browned bits. If using two skillets, divide sherry between them, then transfer onions and liquid to a pot or Dutch oven.

Preparing the Bread and Cheese

6. Preheat broiler and adjust oven rack to the top position. Butter the toasted bread slices and rub them with the garlic clove until fragrant.

Assembling and Broiling

7. Ladle a small amount of broth into the bottoms of 4 ovenproof serving bowls. Place half the toasted bread slices in the bowls.

Cookix's Secrets

Alternative Cooking Methods

Try using a slow cooker for caramelizing onions over several hours.

Bold Flavor Enhancements

Add a splash of brandy or cognac for extra depth.

Broiling

Keep an eye on the cheese while broiling to prevent burning.

Caramelizing Onions

Patience is key—slowly cooking the onions ensures deep flavor development.

Healthier Version

Use vegetable stock and reduce the butter for a lighter version.

Seasonal Tweaks

Use aged Comté cheese instead of Gruyère for a nuttier flavor.

Serving

Use ovenproof bowls to ensure a perfect gratinée effect.

Ask Cookix, your sous-chef