Sauce too thin

Fix it now

In order of preference.

1. Reduce it. Turn the heat up and let it boil uncovered. Water leaves, everything else concentrates, and the flavour improves rather than being diluted. This is always the best answer if you have five minutes.
2. Cornflour slurry. Mix a teaspoon of cornflour with two teaspoons of cold water until completely smooth, stir it into the simmering sauce, and cook for a minute or two. Never tip dry starch into hot liquid.
3. Beurre manié. Mash equal parts soft butter and plain flour into a paste and whisk small pieces into the simmering sauce. Adds richness as well as body. Excellent for gravies and stews.
4. Cream or butter. Whisking cold butter into a sauce off the heat, or adding cream and reducing, thickens by emulsion rather than starch. Best for pan sauces.
5. A starchy addition. A blended cooked potato, a spoonful of pasta water, or some of the dish's own solids blended and returned.

Which thickener for which sauce

Gravy and stew

Beurre manié or a flour-based roux. Robust, and the flour flavour cooks out over a long simmer.

Stir-fry and glossy Asian sauces

Cornflour slurry. It sets clear and shiny and works in under a minute.

Pan sauce for meat

Reduce, then whisk in cold butter off the heat. Never starch.

Tomato sauce

Reduce. Starch dulls it and tomato reduces beautifully.

Fruit sauce or coulis

Reduce, or use a little cornflour. Arrowroot is better still — it sets clearer.

Custard

A different problem entirely — see curdled custard and custard.

Why it went thin

• Too much liquid at the start. The commonest cause, and the one to correct next time rather than now.
• Not simmered long enough. Flour and cornflour both need to reach a proper simmer to thicken fully, and both look thin until they suddenly are not.
• Lid left on. Nothing evaporates under a lid. If a sauce needs to reduce, the lid comes off.
• Watery ingredients. Mushrooms, courgettes, tomatoes and defrosted meat all release a great deal of liquid.
• Too much acid or alcohol added late, which can thin an emulsion and interfere with starch.
• The starch was destroyed. Prolonged boiling, or a lot of acid, breaks flour-thickened sauces down again. Add the acid at the end.

Why reduction beats a thickener

Adding starch makes a sauce thicker and does nothing else. Reducing it makes it thicker by removing water, which means everything that was dissolved in that water is now more concentrated: the sauce gets deeper as well as thicker, and it gains gloss and body a starch cannot give it.

The cost is time and volume. If you need the sauce in ninety seconds, or you need every drop of it, a slurry is the right answer and there is nothing wrong with it. If you have five minutes and a little to spare, reduce.

The other thing reduction does is concentrate salt, so a sauce you intend to reduce should be seasoned at the end rather than the beginning. This is the commonest way a well-made reduction is ruined.

Common questions