📝 About This Recipe
Born in the bustling market stalls of Les Halles, this quintessential French classic is the ultimate testament to the magic of patience and caramelization. This recipe transforms humble yellow onions into a rich, mahogany-hued nectar, deeply flavored with dry sherry and a high-quality beef bone broth. Topped with a crusty baguette crouton and a molten blanket of nutty Gruyère cheese, it is a soul-warming masterpiece that defines comfort food.
🥗 Ingredients
The Onion Base
- 3 pounds Yellow Onions (halved and thinly sliced pole-to-pole)
- 4 tablespoons Unsalted Butter (high-quality European style preferred)
- 1 tablespoon Extra Virgin Olive Oil
- 1/2 teaspoon Granulated Sugar (to assist with caramelization)
- 1 teaspoon Kosher Salt (plus more to taste)
The Deglaze and Broth
- 3 cloves Garlic (minced)
- 1/2 cup Dry Sherry (or dry white wine like Sauvignon Blanc)
- 2 tablespoons All-Purpose Flour
- 6 cups Beef Bone Broth (low sodium, high quality)
- 4 sprigs Fresh Thyme (tied with kitchen twine)
- 1 piece Bay Leaf (dried)
- 1/2 teaspoon Black Pepper (freshly cracked)
- 1 teaspoon Balsamic Vinegar (for a touch of acidity at the end)
The Gratinée Topping
- 1 loaf French Baguette (cut into 1-inch thick rounds)
- 2 cups Gruyère Cheese (freshly grated)
- 1/4 cup Parmigiano-Reggiano (finely grated)
👨🍳 Instructions
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1
In a heavy-bottomed Dutch oven or stockpot, melt the butter with the olive oil over medium-low heat.
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2
Add the sliced onions and toss to coat thoroughly. Cover the pot and cook for 15 minutes to let the onions sweat and soften.
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3
Remove the lid, increase heat to medium, and stir in the salt and sugar. Cook the onions uncovered, stirring every 5-8 minutes.
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4
Continue cooking for 45-60 minutes. The onions will gradually turn from translucent to golden, and finally to a deep, jammy mahogany brown. If they stick too much, add a tablespoon of water to scrape the bottom.
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5
Add the minced garlic and cook for 1-2 minutes until fragrant, being careful not to burn it.
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6
Sprinkle the flour over the caramelized onions and stir constantly for 2 minutes to cook out the raw flour taste.
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7
Pour in the dry sherry to deglaze the pan, using a wooden spoon to scrape up every bit of the brown 'fond' from the bottom of the pot.
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8
Slowly whisk in the beef broth. Add the thyme sprigs and bay leaf. Bring to a boil, then reduce heat to low and simmer for 20-30 minutes.
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9
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 dry and golden.
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10
Remove the thyme sprigs and bay leaf from the soup. Stir in the balsamic vinegar and adjust salt and pepper to taste.
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11
Ladle the hot soup into oven-safe ramekins or bowls, leaving about an inch of space at the top.
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12
Place one or two toasted baguette slices on top of the soup. Generously pile the Gruyère and Parmigiano-Reggiano over the bread, ensuring the cheese reaches the edges of the bowl to create a seal.
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13
Place the bowls on a baking sheet and broil on high for 3-5 minutes, or until the cheese is bubbling and has developed deep brown spots. Serve immediately.
💡 Chef's Tips
Don't rush the onions; the deep flavor comes from the slow caramelization which can take up to an hour. Always grate your own cheese; pre-shredded cheese is coated in starch and won't melt into that iconic gooey pull. Use a combination of beef stock and a splash of chicken stock if you want a lighter, more nuanced flavor profile. If the soup is too sweet from the onions, the teaspoon of balsamic vinegar or a squeeze of lemon juice provides the necessary balance. Ensure your baguette is toasted until quite hard; this prevents it from turning into mush once it hits the soup.
🍽️ Serving Suggestions
Pair with a crisp glass of French Chardonnay or a light-bodied 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 bistro experience. For a lighter lunch, serve in smaller cups alongside half a croque monsieur sandwich. Finish the meal with a light lemon sorbet to cleanse the palate after the savory cheese and broth.