Roux, cornflour or reduction

Three ways to thicken a gravy, what each one does to the taste and the look, and when to use which.

Roux, the British default

Equal weights of fat and plain flour, cooked together before any liquid goes near them. A roux gives an opaque, matt, comforting gravy, the kind that sits properly on mash. It is forgiving, it reheats well, and it is what most people mean when they say gravy.

Cook it for at least a minute after it comes together, longer if you want colour. A pale roux tastes creamy, a golden one tastes nutty, and a dark one tastes toasted but thickens less, which is why dark roux recipes use more flour.

Cornflour, the quick one

Cornflour is mixed with cold liquid into a slurry and stirred into hot gravy at the end. It thickens almost instantly, it is gluten free, and it gives a glossy, slightly translucent finish. That gloss is why chip shop gravy and Chinese brown sauce use it and roast dinner gravy usually does not.

Two catches. Cornflour thins again if you boil it hard for a long time, and it goes claggy and a bit gluey if you overdo it. Add half what you think you need, let it come back to the boil, then judge.

Reduction, the chef's answer

No thickener at all. Boil good stock until enough water has gone that the natural gelatine thickens it on its own. This gives you a jus: glossy, intensely flavoured, clinging to the meat rather than coating it. It is the best tasting option and by far the most expensive in time and stock.

It only works with stock that has real gelatine in it, which means bones and a long simmer. Reducing a stock cube just gives you very salty water.

The other thickeners

Beurre manié is soft butter mashed with an equal weight of flour and whisked into finished gravy in small lumps. It is the emergency fix when a gravy is nearly right but too thin, and it adds a lovely shine.

Blended vegetables thicken beautifully and add flavour rather than dulling it. A couple of ladles of the roasting onions and carrots blitzed with stock will thicken a gravy without any starch at all. Bread, potato and lentils do the same job in older recipes.

So which one

Roast dinner with a proper tin of fat and fond: roux, every time. Weeknight, no time, want it glossy: cornflour. Steak, game, anything where the meat is the point and the sauce should be a whisper: reduction. Gluten free: cornflour or blended veg. Something has gone wrong and it is too thin: beurre manié.