Why the Roux Still Earns Its Place

There are quicker ways to thicken a pan of stock, but none gives quite the same silky, glossy finish as a roux. It is the quiet workhorse behind a proper cheese sauce for cauliflower, the parsley sauce that lifts a piece of poached fish, the onion gravy that soaks into a Sunday roast, and the filling of a fish pie that holds together on the spoon. Two ingredients, equal weights, a few minutes at the hob — that is the whole idea. Learn it once and you will never reach for a packet again.

Equal Weights, Not Guesswork

Weigh rather than spoon. The reliable starting point is equal weights of butter and plain flour — 50g of each, say — which will thicken around 500ml of milk or stock into a coating sauce. Flour varies in how much liquid it absorbs, and butter is easier to measure in grams than in tablespoons, so a small set of scales will always beat an eye.

Melt the butter in a heavy-based saucepan over a medium heat. Let it foam, but do not let it brown if you are after a pale sauce. Tip in the flour all at once and whisk steadily with a small balloon whisk or a wooden spoon. You are looking for a smooth, slack paste that pulls away from the sides of the pan — loose enough to stir easily, thick enough to leave a clean trail. Keep it moving for a minute or two to cook out the raw flour taste.

White, Blond and Brown

How long you cook the roux decides its colour, its flavour and how much liquid it will thicken. Watch the pan rather than the clock, but these timings are a good guide:

• White roux — 1 to 2 minutes. Barely coloured, faintly biscuity. Use for béchamel, cheese sauce, parsley sauce and cream soups.
• Blond roux — 4 to 6 minutes, until it looks like pale sand. Nutty and slightly sweeter. Good for chicken and vegetable gravies.
• Brown roux — 8 to 10 minutes, until it smells like toasted bread. This is the one for beef and onion gravy, but it thickens less, so use about a third more flour or expect a thinner sauce.

Past that point the flour will scorch and turn bitter. If it happens, throw it away and start again — no amount of liquid will repair a burnt roux.

Whisking in the Liquid

The old kitchen rule holds: hot roux takes cold liquid; cold roux takes hot liquid. Either way, add the liquid in stages. Take the pan off the heat, pour in a ladleful of milk or stock, and whisk hard until it disappears into a smooth paste. Add the next ladleful and whisk again. Only once you have a loose, lump-free liquid should you return the pan to the heat and add the rest in a steady stream, whisking all the while.

Bring it to a gentle simmer, then let it bubble quietly for three to five minutes, stirring now and then. This short cook is what gives the sauce its gloss and cooks out any lingering flouriness. Season at the end, never at the start, especially if you are using a stock cube.

Rescuing a Roux That Goes Wrong

Almost every roux fault is fixable, and knowing the fixes saves a whole dinner.

• Lumps: take the pan off the heat and whisk vigorously. If they persist, push the sauce through a fine sieve and return it to the pan.
• Too thick: whisk in warm milk or stock, a splash at a time, until it coats the back of a spoon the way you want.
• Too thin: simmer uncovered to reduce, or mash a knob of butter with an equal amount of flour and whisk that in, a little at a time.
• Split or greasy: off the heat, whisk in a tablespoon of cold milk or a cold knob of butter and it will usually come back together.

Putting It to Work Through the Year

A roux is the base for a dozen everyday dishes, and it adapts neatly to what is in season. In spring, whisk a leek and wild garlic sauce to spoon over new potatoes. Come summer, use it for a sharp Cheddar sauce over cauliflower, or for macaroni cheese with a mustardy edge. In autumn, a blond roux turns cider and stock into a sauce for pork chops, or onions into proper gravy for bangers and mash. Winter is where it earns its keep: a white roux loosened with milk and smoked haddock makes a chowder that warms the whole kitchen, and the same base holds a fish pie together beautifully.

Once you can judge the colour and the thickness by eye, the roux stops being a recipe and becomes a habit. Keep a set of scales by the hob and a whisk within reach, and you have the foundation of half the sauces in the British kitchen.