Equipment
Ingredients
Aromatics and Fat
- 1000 g yellow onions, sliced uniformly, about 3mm thick
- 50 g unsalted butter
- 15 ml olive oil
Soup Base
- 15 g all-purpose flour
- 120 ml dry white wine
- 1000 ml high-quality beef stock
- 2 fresh thyme
- 1 bay leaf, dried
- 5 g kosher salt
- 2 g black pepper, freshly ground
Gratinee
- 150 g french baguette, cut into thick slices
- 200 g gruyere cheese, coarsely grated
- 1 garlic, peeled, halved
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 578 kcal
- Protein
- 24 g
- Carbohydrates
- 47 g
- Fat
- 31 g
- Fiber
- 6 g
- Sugar
- 11 g
- Sodium
- 1926 mg
- Saturated Fat
- 17 g
- Monounsaturated Fat
- 11 g
- Polyunsaturated Fat
- 2 g
- Cholesterol
- 82 mg
- Potassium
- 644 mg
- Calcium
- 606 mg
- Iron
- 1.6 mg
- Magnesium
- 74 mg
- Phosphorus
- 482 mg
- Zinc
- 2.9 mg
- Vitamin A
- 222 mcg
- Vitamin C
- 20 mg
- Vitamin D
- 0.3 mcg
- Vitamin E
- 1.1 mg
- Vitamin K
- 7 mcg
- Vitamin B6
- 0.5 mg
- Vitamin B12
- 1.0 mcg
- Thiamin
- 0.36 mg
- Riboflavin
- 0.37 mg
- Niacin
- 3.9 mg
- Folate
- 96 mcg
- Water
- 528 g
- Alcohol
- 3 g
Sources: USDA FoodData Central
Method
Melt the butter and olive oil in a large heavy-bottomed pot over medium heat. Add the sliced onions and toss to coat in the fats.
Reduce the heat to medium-low. Cook the onions, stirring occasionally at first and more frequently as they darken, until they collapse into a deep, rich mahogany paste. This slow caramelization is crucial and cannot be rushed.
Sprinkle the all-purpose flour over the caramelized onions and stir continuously to cook out the raw flour taste.
Pour in the dry white wine to deglaze the pot, scraping up all the browned bits from the bottom. Allow the wine to evaporate almost entirely.
Stir in the beef stock, thyme sprigs, bay leaf, kosher salt, and black pepper. Bring the liquid to a gentle simmer and let the flavors meld.
While the soup simmers, preheat the oven to 200°C (400°F). Arrange baguette slices on a baking sheet and toast until dry and lightly golden. Remove from oven and immediately rub one side of each slice with the cut side of the raw garlic halve.
Remove the thyme sprigs and bay leaf from the soup. Ladle the hot soup into oven-safe bowls, leaving about 2 centimeters of space at the top. Float 1 or 2 toasted, garlic-rubbed baguette slices on the surface of each bowl.
Mound the grated Gruyere generously over the top of the bread, allowing it to spill slightly over the edges of the bowls to form a crust when melted. Place the bowls on a baking sheet.
Broil in the oven at 260°C (500°F) until the cheese is bubbling vigorously and features dark brown, crusty spots.
Chef's Notes
- Patience is your greatest ingredient here. Rushing the caramelization process will result in boiled onions rather than sweet, jammy ones, fundamentally altering the soup's flavor profile.
- Because the ingredient list is quite minimal, the quality of your beef stock dictates the final caliber of the dish. A gelatin-rich, homemade stock yields an incredible mouthfeel.
- Rubbing the toasted baguette with a raw garlic clove adds a sharp, aromatic bite that beautifully cuts through the intensely rich, fatty cheese topping.
Storage
Refrigerator: 4 days — Store soup base only. Do not store assembled with bread and cheese.
Freezer: 3 months — Freeze soup base in an airtight container.
Reheating: Reheat the soup base gently on the stovetop until simmering, then assemble in oven-safe bowls with fresh toast and cheese and broil as instructed.
Troubleshooting
Onions are burning and turning bitter
Cause: Heat is too high or stirring is too infrequent during the caramelization process
Fix: Lower the heat immediately and add 15 to 30ml of water to cool the pan down and dissolve any scorched bits
Prevention: Maintain a medium-low heat and stir more frequently as the onions reduce in volume
Bread sinks to the bottom of the bowl
Cause: Bread was not toasted enough or was sliced too thinly
Fix: Cannot be fixed once assembled, but still tastes delicious
Prevention: Ensure baguette slices are at least 1.5 centimeters thick and toasted until completely dry and hard
Broth lacks depth and tastes watery
Cause: Onions were not caramelized long enough or stock quality was poor
Fix: Simmer uncovered for an additional 15 minutes to reduce and concentrate the flavors before assembling
Prevention: Commit to the full 45 minutes of onion caramelization and use a high-quality stock
Cultural Context
Originating in Paris in the 18th century, Soupe a l'oignon was historically considered food for the poor due to the cheap abundance of onions. It achieved legendary culinary status when it became the restorative late-night meal of choice served in the bustling markets of Les Halles to feed weary workers and revelers alike.
