This iconic French classic features caramelized onions simmered in rich beef broth until deeply golden and sweet, topped with crusty bread and melted Gruyère cheese. The magic happens when those humble onions transform through patient cooking into a luxurious, velvety soup that warms the soul with every spoonful. Perfect for a cozy dinner or elegant starter that tastes far more complicated than it actually is.
⏱️90 min
📊Medium
👥4 servings
🍽️Soup
vegetarianbudget-friendlyfamily
Ingredients
1500 gyellow onions
60 gbutter
1000 mlbeef broth
200 mldry white wine
200 gGruyère cheese
1 piecebaguette or crusty bread
3 sprigsfresh thyme
1 piecebay leaf
5 gsalt
3 gblack pepper
Instructions
1PREPARE THE ONIONS: Peel and slice all 1500g of yellow onions into thin, even half-moon slices approximately 5mm thick. Ensure consistent thickness so they cook evenly and caramelize uniformly. This step takes patience but is crucial for the soup's final texture and flavor development.
2MELT THE BUTTER: Heat 60g of butter in a large, heavy-bottomed pot or Dutch oven over medium heat until it foams and turns light golden, about 1-2 minutes. Add all the sliced onions and stir well to coat them evenly with the butter. The pot should be large enough to accommodate the onions comfortably, though they will reduce significantly during cooking.
3CARAMELIZE THE ONIONS: Cook the onions uncovered for 40-50 minutes, stirring occasionally (every 8-10 minutes) to ensure even browning and prevent burning on the bottom. The onions will first release their moisture and become translucent (about 15 minutes), then gradually turn golden and finally develop deep caramel color. You'll know they're ready when they're a rich brown color and have reduced to about one-quarter of their original volume, with a sweet, nutty aroma filling your kitchen.
4DEGLAZE WITH WINE: Pour 200ml of dry white wine into the caramelized onions, scraping the bottom of the pot with a wooden spoon to lift all the flavorful browned bits (fond). Let the wine simmer for 2-3 minutes until it reduces by about half and the raw alcohol smell dissipates, leaving only the wine's rich flavor. This step adds complexity and depth to your soup's flavor profile.
5BUILD THE BROTH: Add 1000ml of beef broth, 3 sprigs of fresh thyme, and 1 bay leaf to the pot with the onions. Season with 5g of salt and 3g of black pepper. Bring the mixture to a gentle simmer over medium-high heat, then reduce heat to low and simmer uncovered for 15-20 minutes, allowing the flavors to meld together. The soup should bubble gently at the edges but not boil vigorously, which would evaporate too much liquid.
6PREPARE THE BREAD AND CHEESE: While the soup simmers, slice your baguette or crusty bread diagonally into 4 thick slices about 2cm wide. Arrange them on a baking sheet and bake in a 200°C (400°F) oven for 5-7 minutes until golden and crispy but not completely hard, as they'll absorb the soup's liquid. Grate 200g of Gruyère cheese and set it aside, having slightly more than you think you'll need.
7ASSEMBLE AND BROIL: Remove the thyme sprigs and bay leaf from the soup and discard them. Taste the soup and adjust seasoning as needed with additional salt and pepper. Ladle the hot soup into individual oven-safe bowls, place one toasted bread slice on top of each, and generously pile the grated Gruyère cheese on top, covering the bread completely. Place the bowls on a baking sheet and broil under high heat 10-15cm from the heating element for 3-5 minutes until the cheese is melted, bubbly, and slightly golden at the edges, being careful not to let it burn. Serve immediately while the cheese is still hot and stringy.