La Soupe A L'oignon Recipe
Classic French onion soup with croutons and Gruyere cheese.
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Ingredients
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Soup
Croutons & Topping
Method
Soup
Caramelize onions
In a large heavy-bottomed pot or Dutch oven over medium heat, melt the butter with the oil. Add the sliced onions and spread them evenly. Sprinkle with the salt and sugar. Cook, stirring every 3–5 minutes, adjusting heat as needed so the onions soften and progressively brown without burning. This process will take 40–55 minutes. If the pan browns too quickly, reduce heat; if the onions stick, add a tablespoon of water to deglaze and loosen browned bits.
Deglaze and build flavor
When the onions are a deep golden-brown and jammy, sprinkle the flour over them and stir for 1–2 minutes to cook the raw flour taste and help thicken slightly. Pour in the white wine and sherry (if using) and scrape the bottom of the pot with a wooden spoon to lift browned bits. Let the alcohol bubble off for about 2 minutes.
Simmer soup
Add the beef and chicken stocks, thyme sprigs, and bay leaves. Bring to a gentle simmer, reduce heat to low, and simmer, uncovered, for 20–25 minutes to meld flavors. Taste and adjust seasoning with salt and freshly ground black pepper. Remove thyme sprigs and bay leaves before serving.
Croutons & Assembly
Make croutons
Preheat oven to 200°C (400°F). Arrange baguette slices on a baking sheet, brush both sides lightly with olive oil, and toast for 6–8 minutes, flipping halfway, until golden and crisp. When warm, rub the top of each slice with the halved garlic clove for a subtle garlic aroma.
Assemble bowls
Ladle the hot soup into ovenproof bowls or crocks, filling them to about 3/4 full. Float 1–2 toasted baguette slices on each bowl of soup (they will soak up some broth). Generously top each bowl with a layer of grated Gruyère (about 40–60 g per serving). Sprinkle a little grated Parmesan on top if using.
Grill cheese
Place the filled bowls on a baking sheet and broil (or place under a salamander) until the cheese is fully melted, bubbling, and golden-brown in spots — about 3–6 minutes depending on broiler strength. Watch carefully to avoid burning. Alternatively, finish under a preheated 220°C (425°F) oven for 6–10 minutes.