Classic French Onion Soup with Gruyère Gratinée
Deeply caramelized yellow onions simmered in rich beef bone broth, topped with crusty French baguette and bubbly melted Gruyère cheese.
In a nutshell: Classic French onion soup features slow-caramelized sweet yellow onions simmered in savory beef bone broth with white wine and thyme, topped with crusty French baguette and broiled bubbly golden Gruyère cheese.
The quintessential French bistro classic. Thinly sliced yellow onions slowly caramelized to sweet golden perfection with butter, deglazed with dry white wine, and simmered in an aromatic beef herb broth. Broiled under a crust of toasted French bread and bubbling Gruyère cheese.
Key Equipment
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- Heavy Dutch Oven or Pot
- Oven-Safe Soup Crocks
- Wooden Spoon
- Chef's Knife & Cutting Board
Chef's Pro-Tips
- Patience with Onions: True French onion flavor comes from slow caramelization (40+ minutes). Rushing the onions on high heat scorches them bitter rather than naturally sweet.
- Stale Baguette Toasting: Bake baguette slices dry at 375°F (190°C) for 8 minutes before assembling. Dried bread absorbs the broth without disintegrating into mush.
- Quality Broth: Using rich beef bone broth provides rich body and natural gelatin that gives French bistro soup its luxurious mouthfeel.
Ingredients
4
servings
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3 lbs yellow onions, halved and thinly sliced (approx. 5-6 large onions)
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3 tbsp unsalted European butter
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1 tbsp extra virgin olive oil
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½ tsp granulated sugar, helps caramelization
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4 cloves garlic, minced
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½ cup dry white wine (Sauvignon Blanc or Pinot Grigio), or dry French vermouth
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6 cups rich beef bone broth, high gelatin content
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2 sprigs fresh thyme, tied with kitchen twine
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1 whole bay leaf
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1 tbsp Worcestershire sauce
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8 slices French baguette, approx 1/2-inch thick, toasted dry
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2 cups Gruyère cheese, freshly grated, plus 2 tbsp grated Parmesan
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Step-by-Step Instructions
Slow-Caramelize the Onions
Melt butter and olive oil in a heavy Dutch oven or large enamel pot over medium-low heat. Add sliced yellow onions and toss to coat thoroughly. Cook uncovered for 15 minutes, stirring occasionally. Sprinkle with 1/2 teaspoon sugar and 1 teaspoon kosher salt. Reduce heat to low and continue cooking for 35-40 minutes, stirring every 5 minutes to scrape fond from the pan bottom, until onions collapse into a deep, jammy mahogany golden-brown.
Deglaze with White Wine
Add minced garlic and cook for 1 minute until fragrant. Pour in dry white wine, using a wooden spoon to vigorously scrape up all browned bits stuck to the bottom of the pot. Simmer gently for 2-3 minutes until the alcohol cooks off and the wine is nearly completely reduced.
Simmer Beef Broth & Aromatics
Pour in beef bone broth and Worcestershire sauce. Add fresh thyme sprigs and bay leaf. Bring to a gentle boil, then lower the heat and simmer uncovered for 20 minutes so the broth absorbs the deep sweetness of the caramelized onions. Remove thyme sprigs and bay leaf; taste and season with black pepper and salt if needed.
Assemble & Broil Gratins
Preheat your oven broiler to High. Arrange 4 oven-safe ceramic soup crocks or bowls on a sturdy rimmed baking sheet. Ladle piping hot soup into each crock, leaving 1/2 inch of space at the top. Float 1-2 slices of toasted baguette on top of each bowl. Generously mound grated Gruyère cheese and a touch of Parmesan over the bread, allowing some cheese to drape over the bowl rims.
Broil to Golden Perfection
Transfer baking sheet directly under the broiler (about 5-6 inches from heating element). Broil for 3-4 minutes until cheese is bubbly, melted, and browned with rich caramelized spots. Carefully remove with heat-proof oven mitts, let rest for 3 minutes, garnish with fresh thyme leaves, and serve warm.
Chef Clara's Kitchen Picks
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View on AmazonFrequently Asked Questions
Gruyère is the gold standard because of its nutty, savory profile and exceptional melting qualities. You can also mix Gruyère with Swiss Emmental or sharp fontina.
Yes! Simply omit the white wine and deglaze the caramelized onions with an extra 1/2 cup of beef broth mixed with 1 teaspoon of apple cider vinegar.
The soup base actually tastes even better the next day as the caramelized onions harmonize with the beef broth. Reheat the broth thoroughly before ladling into crocks and broiling the cheese.
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