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Onions in gravy

The most important vegetable in the jug

From Gravypedia, the encyclopaedia of gravy

🕑 History Last edited 2026-09-21 👁 9 views #aromatics#caramelisation#onion

Onions contribute sweetness, body and colour to gravy — but only if cooked long enough for their sugars to caramelise.

If you change one thing about your gravy, cook the onions for longer.

Why they work

Onions contain fructans and other sugars. Cooked slowly, these break down and caramelise, producing sweetness and hundreds of brown-flavour compounds. They also soften into a purée that thickens gravy without flour, and their colour darkens the finished sauce.

Cooked quickly, none of that happens — you get fried onion flavour, which is a different and lesser thing.

The timings

Time State Use
5 min Softened, translucent Adequate base for a quick gravy
10–12 min Golden at the edges The realistic weeknight compromise
25–30 min Deep brown, jammy, collapsed Proper onion gravy
45+ min Almost a purée, very sweet French onion soup territory

How to do it properly

  1. Slice thinly and evenly. Thick chunks cook unevenly.
  2. Use a wide pan — crowded onions steam.
  3. Medium-low heat, butter with a little oil to stop it burning.
  4. A pinch of salt at the start draws out water and speeds things up.
  5. Stir every few minutes, scraping the browned film off the base back into the onions.
  6. If they threaten to catch, add a splash of water and scrape.

⚠️ Watch out

Burnt onion is bitter and the bitterness spreads through the whole gravy. There is no rescue. Turn the heat down rather than risking it.

Which onion

Brown/yellow onions are the default: enough sugar to caramelise, enough structure to hold. Red onions are sweeter and go slightly grey-purple in a pale gravy. Shallots are finer and sweeter, and are the classic choice for a jus. Spring onions are for finishing, not for the base.

In or out?

An onion gravy keeps its onions. A roast gravy usually strains them out, having taken their flavour — see straining and skimming gravy. Either is correct; decide before you slice, because strained gravy is better with thick slices and onion gravy with thin ones.

See also

More in Ingredients

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