📝 About This Recipe
This quintessential French classic is a masterclass in patience, transforming humble yellow onions into a rich, mahogany elixir through slow caramelization. Originating in the markets of Paris, this soup balances the savory depth of beef bone broth with the sweetness of melt-in-your-mouth onions and a splash of dry sherry. Topped with a crusty baguette slice and a bubbling blanket of nutty Gruyère cheese, it is the ultimate comfort food for a sophisticated dinner.
🥗 Ingredients
The Onion Base
- 3 pounds Yellow Onions (thinly sliced pole-to-pole)
- 4 tablespoons Unsalted Butter (high quality)
- 1 tablespoon Olive Oil
- 1/2 teaspoon Granulated Sugar (to aid caramelization)
- 1 teaspoon Kosher Salt (plus more to taste)
The Broth and Aromatics
- 3 cloves Garlic (minced)
- 1/2 cup Dry Sherry (or dry white wine like Sauvignon Blanc)
- 6 cups Beef Stock (high-quality, low-sodium)
- 2 tablespoons All-purpose Flour
- 4 sprigs Fresh Thyme (tied with kitchen twine)
- 1 piece Bay Leaf (dried)
- 1/2 teaspoon Black Pepper (freshly cracked)
The Gratinée
- 1 loaf French Baguette (cut into 1-inch thick slices)
- 2 cups Gruyère Cheese (freshly grated)
- 1/4 cup Parmesan Cheese (freshly grated)
👨🍳 Instructions
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1
In a large, heavy-bottomed Dutch oven, melt the butter with the olive oil over medium heat. The oil prevents the butter from burning during the long cook time.
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2
Add the sliced onions to the pot and toss to coat thoroughly with the fat. Cover the pot and cook for 10 minutes until the onions have softened and released their moisture.
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3
Remove the lid. Stir in the salt and sugar. Increase the heat slightly to medium-high and cook, stirring every few minutes, for about 45-60 minutes.
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4
Monitor the onions closely; they should turn a deep, uniform mahogany brown. If they stick too much, add a tablespoon of water to deglaze the bottom of the pan.
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5
Once the onions are jammy and dark brown, add the minced garlic and cook for 1 minute until fragrant.
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6
Sprinkle the flour over the onions and stir constantly for 2 minutes. This 'roux' will help slightly thicken the soup and provide a silky mouthfeel.
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7
Pour in the dry sherry to deglaze the pan, using a wooden spoon to scrape up all the flavorful brown bits (fond) from the bottom.
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8
Slowly stir in the beef stock, thyme sprigs, and bay leaf. Bring the mixture to a boil, then reduce heat to low.
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9
Simmer the soup partially covered for 30 minutes to allow the flavors to meld. Remove the thyme sprigs and bay leaf before serving.
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10
While the soup simmers, preheat your oven to 400°F (200°C). Arrange baguette slices on a baking sheet and toast for 5-7 minutes until golden and crisp.
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11
Taste the soup and adjust seasoning with salt and plenty of freshly cracked black pepper. Ladle the hot soup into oven-safe crocks or bowls.
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12
Place one or two toasted baguette slices on top of each bowl. Generously heap the Gruyère and Parmesan over the bread, allowing some to spill over the edges.
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13
Place the crocks on a baking sheet and broil for 2-4 minutes, or until the cheese is melted, bubbly, and has developed brown toasted spots. Serve immediately.
💡 Chef's Tips
Do not rush the onions; the deep flavor comes entirely from the slow caramelization process which cannot be faked. Use a mix of yellow and red onions for a more complex sweetness if desired. Always grate your own cheese; pre-shredded cheese is coated in potato starch and won't melt as smoothly. For an extra layer of flavor, rub a raw garlic clove onto the toasted baguette slices before placing them on the soup. If you don't have oven-safe bowls, melt the cheese on the toast in the oven first, then float them on the soup.
🍽️ Serving Suggestions
Pair with a glass of crisp dry white wine or a medium-bodied red like Pinot Noir. Serve alongside a simple green salad with a sharp Dijon vinaigrette to cut through the richness. A side of roasted marrow bones adds an extra layer of decadence for a full dinner course. Finish the meal with a light fruit tart or lemon sorbet to cleanse the palate.