French Onion Soup with Cheese
All the flavour of French onion soup comes from the slow caramelisation that takes 45 minutes over low heat. Any shortcut gives you ordinary onion soup — the onion must turn deep brown and sweeten before the liquid goes in.
- Prep
- 15 min
- Cook
- 65 min
- Total
- 80 min
- Calories
- 340
Onion soup is one of the cheapest and best-known French soups, and almost all of it is onion. Which is why there is no room for shortcuts — time is the main ingredient.
Method
-
1
Slice the onion
Cut the onion into thin, even slices of the same thickness. Uneven slices caramelise at different rates, so some burn while others stay raw.
⏱ 12 min -
2
Start the caramelisation
Melt the butter with the oil and add the onion, salt and sugar over medium heat for 10 minutes, stirring. The onion will release water first — let it evaporate.
⏱ 11 min -
3
Slow caramelisation
Lower the heat and continue for 35 minutes, stirring every 5 minutes. The onion must reach a deep brown rather than golden — that is the entire source of flavour.
⏱ 36 min -
4
Deglaze
When the base browns, add a little stock and scrape the base with a wooden spoon. That brown layer is called fond and is packed with concentrated flavour.
⏱ 4 min -
5
Flour and liquid
Sprinkle in the flour and stir for two minutes, then pour in the stock with the bay and thyme and simmer for 20 minutes. Add the vinegar at the end.
⏱ 23 min -
6
Toast and cheese
Toast the bread slices, ladle the soup into ovenproof bowls, and set the bread and cheese on top. Under the grill for 4 minutes until the cheese melts and browns.
⏱ 9 min
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Tips that actually matter
- 45 minutes of caramelisation is not optional — any shortcut gives ordinary onion soup.
- Evenly thick slices, or some burn while others stay raw.
- Scrape the browned base — it is the richest part of the flavour.
- A spoonful of vinegar at the end lifts the whole dish and balances the onion's sweetness.
People also ask
Why does my onion soup taste ordinary?
The onion was not caramelised enough. It needs 45 minutes over low heat to reach a deep brown. Pale gold means you are only halfway — the sweetness and depth arrive in the last 15 minutes.
Can I speed up the caramelisation?
A little: a spoonful of sugar and a small pinch of bicarbonate speed the reaction by 10-15 minutes. But there is no real shortcut — the onion needs time for its sugars to caramelise.
What replaces Gruyère?
Mozzarella with a little parmesan gives a close result: the mozzarella melts and the parmesan brings the sharpness. Gruyère does both, but this substitute works well.
Cook mode
French Onion Soup with Cheese
-
1
Slice the onion
Cut the onion into thin, even slices of the same thickness. Uneven slices caramelise at different rates, so some burn while others stay raw.
-
2
Start the caramelisation
Melt the butter with the oil and add the onion, salt and sugar over medium heat for 10 minutes, stirring. The onion will release water first — let it evaporate.
-
3
Slow caramelisation
Lower the heat and continue for 35 minutes, stirring every 5 minutes. The onion must reach a deep brown rather than golden — that is the entire source of flavour.
-
4
Deglaze
When the base browns, add a little stock and scrape the base with a wooden spoon. That brown layer is called fond and is packed with concentrated flavour.
-
5
Flour and liquid
Sprinkle in the flour and stir for two minutes, then pour in the stock with the bay and thyme and simmer for 20 minutes. Add the vinegar at the end.
-
6
Toast and cheese
Toast the bread slices, ladle the soup into ovenproof bowls, and set the bread and cheese on top. Under the grill for 4 minutes until the cheese melts and browns.
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