How do I caramelise onions properly?
Why it takes forty minutes rather than the ten most recipes claim, and how to get there without burning them.
- Difficulty
- beginner
- Time
- 45 min
- Read
- 2 min
Short answer
Slice thinly, cook over medium-low heat with a pinch of salt, and stir every few minutes for 30-45 minutes. Recipes that say ten minutes are describing softened onions, not caramelised ones.
Caramelising is sugars browning slowly, and it genuinely cannot be rushed. High heat gives you browned edges and raw centres, which tastes quite different from the deep sweetness of properly caramelised onions.
What you'll need
- Onions
- Wide heavy pan
- Butter or oil
- Salt (optional)
Step by step
- Slice the onions thinly and evenly.Thin slices have more surface area and cook evenly. Uneven pieces mean some are burnt while others are still raw.
- Use a wide pan so they are not piled deep.Depth traps steam and they stew rather than brown. A wide pan is the difference between forty minutes and ninety.
- Start over medium heat with butter or oil and a pinch of salt.Salt draws water out, which speeds the early stage considerably.
- Drop to medium-low once they have softened.About ten minutes in. From here it is a slow process and any attempt to hurry it burns the edges.
- Stir every few minutes, scraping the base.The browning happens against the pan. Scraping it back in is what distributes the colour and flavour.
- Deglaze with a splash of water when the base darkens.A tablespoon of water lifts the fond back into the onions. Repeat whenever the pan looks like it might catch.
- Keep going for 30-45 minutes.They should be deep brown, jammy and sweet. At twenty minutes they are golden and softened, which is a different thing.
- Freeze what you do not use.In an ice cube tray. Since it takes forty minutes, making a large batch is far more efficient than making them per meal.
Tips
- Adding sugar speeds the colour but not the flavour development. It looks caramelised without tasting it.
- A small splash of balsamic or sherry vinegar at the end lifts them and stops the sweetness being cloying.
- Bicarbonate of soda speeds browning dramatically but can give a slightly soapy taste and a mushy texture. Use a tiny pinch if at all.
Common mistakes
- Cooking them on high heat to save time — The edges burn while the centres stay raw. It tastes bitter rather than sweet, and it cannot be corrected.
- Piling them deep in a small pan — They release steam with nowhere to go and stew instead of browning, which takes far longer overall.
- Stopping at twenty minutes — That is softened, not caramelised. The deep sweetness only develops in the last fifteen minutes.
Questions people ask
How long does it take to caramelise onions?
Thirty to forty-five minutes over medium-low heat. Recipes claiming ten minutes are describing softened onions, which taste noticeably different.
Can you caramelise onions faster?
Not really. Salt and a wide pan help, and a pinch of bicarbonate of soda speeds it but affects the texture and taste. The flavour development genuinely needs the time.