What is beurre manié and when is it better than a roux?

A roux is made at the start, before the liquid. A beurre manié is the same two ingredients used at the end, after you have discovered the sauce is too thin. That single difference makes it the most useful thickening trick in a domestic kitchen, because thinness is almost always discovered late.

What you'll need

• Soft butter
• Plain flour
• A fork or your fingers

Step by step

1. Weigh equal amounts of soft butter and plain flour.15g of each will noticeably thicken 500ml of sauce; 25g of each will take it to a coating consistency. The butter must be genuinely soft — straight from the fridge it will not combine.
2. Work them into a completely smooth paste.A fork on a saucer, or between your fingers. There should be no dry flour visible and no streaks. Every particle of flour needs a coat of fat around it, because that coating is what stops it lumping.
3. Bring the sauce to a gentle simmer.The flour will not thicken below about 60°C. Whisking it into a lukewarm sauce leaves you with a slick of butter and no thickening until it heats, at which point it can seize.
4. Whisk in pea-sized pieces, one at a time.Each piece melts, the fat disperses and the flour is released into the liquid already separated. Wait until one has fully disappeared before adding the next, and stop when the sauce is slightly thinner than you want.
5. Simmer for two minutes after the last piece.This is not optional. The flour needs cooking or the sauce tastes raw and pasty, and it also has not reached full thickness until it has simmered.
6. Taste and adjust.You have added unsalted butter and flour, so the sauce is very slightly diluted in flavour. It will usually want a pinch of salt and it will be glossier and richer than before.

Tips

• Make a batch, roll it into a sausage in cling film, and freeze it. Slice off a coin whenever a stew, casserole or gravy comes out thin.
• It enriches as well as thickens. A stew finished with beurre manié tastes rounder as well as being thicker, which is why it is worth using in preference to a slurry in a braise.
• Do not use it in a sauce that is already very fatty. You are adding butter, and a greasy sauce will get greasier.
• The paste can be flavoured — with anchovy, mustard, herbs or garlic — so it seasons and thickens in one move.
• If a sauce is too thin because it is watery rather than under-thickened, reduce it instead. Thickening a watery sauce gives you a thick watery sauce.

Alternatives

• Roux: The same ingredients cooked in the pan first, before the liquid. Better when you are building a sauce from scratch and know how thick you want it, and the only sensible option for a large quantity such as a lasagne béchamel.
• Cornflour slurry: Faster and glossier, and it adds no fat. But it thins if the sauce is held, reheated or frozen, and it makes the sauce translucent rather than creamy. Better for stir-fries, worse for a gravy you will keep.
• Reduction: Adds nothing at all and concentrates flavour, but it takes time and it concentrates salt. Right when the sauce is under-seasoned; wrong when it is already well seasoned or already salty.
• Beurre manié with cornflour: The same paste made with cornflour instead of flour thickens harder and faster and stays clearer. It inherits cornflour's weaknesses on reheating, so use it only for a sauce being served immediately.

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