French onion soup: caramelised onion, stock, toast under a cheese crust
A kilo of onions, butter, patience and stock: that is the whole recipe. Onions cooked for three-quarters of an hour turn into sweet brown caramel, stock makes an amber soup of them, and a cheese toast grilled on top finishes it. Rushing the caramelising is the worst mistake you can make here, and unfortunately the most common.
Your own work in that: 10 min.
- Slicing 10 min
- Onions caramelising 45 min
- Soup simmering 25 min
- Grilling 10 min
Step by step
0 / 6 doneSlice the onions thinly
Peel the onions, halve and slice into thin half-rings, 2–3 mm. A kilo is a big pile; in the pot it shrinks several times over. A sharp knife and an open window.
Ingredients: 1000 g onions · 50 g butter · 1 tbsp oil · 1 pinch sugar · 1 tsp salt · 1 tbsp plain flour · 1200 ml beef or vegetable stock · 1 pcs bay leaf · 1 tbsp wine vinegar · ½ tsp black pepper
Thin half-rings, a whole mountainStart in butter
Melt the butter with the oil in a wide, heavy pot over medium heat. Add the onions, salt and a pinch of sugar, stir. For the first 10 minutes the onions release water and soften; stir every few minutes.
The mountain softens and sinksCaramelise slowly
Lower the heat to low and keep cooking 35 minutes, stirring every 4–5 minutes and scraping the brown film from the base. The onions should go from pale, through golden, to deep brown, soft and sweet. If they start to catch, add a spoon of water and scrape. Don't raise the heat to hurry: burnt onion is bitter, not caramel.
TipCaramelising is not frying. Onion sugars break down slowly at low temperature; over high heat the edges burn while the middle stays raw. Three-quarters of an hour is the minimum, an hour is better still.
After 45 minutes: brown, soft, sweetFlour, vinegar, stock
Sprinkle the onions with flour and fry a minute, stirring. Pour in the vinegar (or wine) and scrape the base clean. Pour in the hot stock, add the bay leaf and pepper. Simmer 25 minutes. Taste: the soup should be sweet-salty with a little acid.
Stock over the caramel, twenty-five minutesMake the toasts
Meanwhile toast the baguette slices in a dry pan or the oven until crisp on both sides. Grate the cheese coarsely. Turn the oven grill on to 220 °C.
Ingredients: 8 pcs baguette · 150 g hard cheese, grated
Crisp slices, grated cheeseGrill under the cheese
Ladle the soup into ovenproof bowls, put two toasts on each and cover thickly with cheese, so it hangs over the rim. Put under the grill 5–8 minutes, until the cheese melts and browns in bubbles. Serve at once, warning that the bowls are scalding.
TipNo ovenproof bowls: grill the cheese toasts separately on a tray and lay them on the soup just before serving. Less dramatic, the same flavour.
Cheese browned in bubbles, bowls scalding
Before you start
Make ahead
Caramelise 2 kg of onions at once and freeze half in portions. Soup from frozen onions takes 30 minutes instead of an hour and a half.
With thyme and wine
A sprig of thyme in the stock and 100 ml dry white wine instead of vinegar: the French bistro version.
Bitter onions
Heat too high and the edges burnt. It can't be undone; next time lower heat, more frequent stirring, a spoon of water when the base darkens too fast.
