French Onion Soup
An hour of patient onions, a dark broth and a bubbling cheese lid
- Serves
- 4
- Hands-on
- Total
- Level
- Some skill
Almost the whole flavor of this soup comes from onions slowly cooked until they are a deep, sticky brown. This version uses a mix of beef and chicken stock for depth without heaviness, a splash of dry white wine for brightness, and a thick toast crowned with Gruyère under the grill.
Ingredients
Soup
- 40 gunsalted butter (3 tbsp)
- 1⅓ kgyellow onions (2¾ lb)about 7 medium, halved and thinly sliced pole to pole
- 5 gfine sea salt (¾ tsp)plus more to taste
- 1 tbspall-purpose flour
- 150 mldry white wine (⅔ cup)or dry sherry
- 750 mlbeef stock (3 cups)Brown Stock or good store-bought
- 500 mlchicken stock (2 cups)Chicken Stock or good store-bought
- 4 sprigsthyme
- 1bay leaf
- 1 tspsherry vinegaror red wine vinegar
- black pepper
Topping
- 4 slicescountry bread or baguette2 cm thick, cut to fit your bowls
- 160 gGruyère or Comté (1¾ cups grated)coarsely grated
- Allergens
- gluten, milk, celery, sulphites
- Origin
- France
- Season
- Autumn, Winter
Method
- Melt the butter in a wide heavy pot over medium heat. Add the onions and salt; the pot will be very full. Cover and cook 10 minutes, stirring twice, until the onions have collapsed and released their liquid.
- Uncover and cook over medium to medium-low heat, stirring every few minutes and scraping the brown film off the bottom, until the onions are a deep mahogany, soft and jammy, 45–60 minutes. If the bottom starts to scorch rather than brown, add 2 tbsp water and scrape.
- Sprinkle over the flour and stir for 1 minute.
- Pour in the wine and scrape the pot clean. Boil until nearly evaporated, about 2 minutes.
- Add both stocks, the thyme and bay leaf. Simmer gently, partly covered, for 20 minutes. Remove the herbs, stir in the vinegar, and season with salt and pepper.
- While the soup simmers, heat the oven grill (broiler) to high. Toast the bread on a sheet pan until dry and pale gold on both sides, 2–3 minutes per side.
- Set 4 ovenproof bowls on the sheet pan. Ladle in the hot soup, float a toast on each, and pile the cheese on top so it covers the bread and reaches the rim.
- Grill 10–15 cm from the element until the cheese is bubbling and browned in spots, 3–5 minutes. Watch closely. Serve with a warning about the hot bowls.
Why it works
Onions are full of sugars and amino acids; slow, even heat drives both Maillard browning and caramelization, building hundreds of new savory and bitter-sweet compounds. Covering at first steams the onions limp so they brown evenly instead of burning at the edges. The brown film (fond) left on the pot is concentrated flavor, so each scrape returns it to the onions. A drop of vinegar at the end sharpens the sweetness so the soup tastes deep rather than sugary.
Common mistakes
- Rushing the onions over high heat: they burn at the edges before the center browns, and the soup turns bitter. Give them the full time.
- Using a narrow pot: the onions steam in a deep layer and never brown. Use your widest heavy pot.
- Too-thin bread: it dissolves. Cut it thick and toast it dry first.
Variations
- All-vegetable version
- Use Vegetable Stock and add 1 tbsp soy sauce and 1 tsp Marmite or miso for the savory depth beef stock gives.
Make ahead and storage
Cook the onions up to 3 days ahead, or make the whole soup and refrigerate up to 4 days or freeze 3 months. Add toast and cheese only at serving.
Notes
No ovenproof bowls: grill the cheese on the toasts on a sheet pan and float them on the soup. Short-cut: start with 400 g Caramelized Onions (about 1⅓ batches) and begin at the flour step.
