Béchamel (White Sauce)

One of the five mother sauces of classic cooking and probably the most useful one for everyday cooking. It's just three ingredients — butter, flour and milk — but the technique is everything: a well-cooked roux and milk added gradually give you a smooth, glossy, lump-free sauce. Use it as a base for lasagna and gratins, to fill pancakes and croquettes, or turn it into cheese sauce (mornay) by stirring in grated cheese at the end.

Ingredients

500ml whole milk
30g butter (about 2 tablespoons)
30g all-purpose flour (about 3 level tablespoons)
1/2 teaspoon salt
White or black pepper to taste
1 pinch freshly grated nutmeg

Optional (to infuse the milk)

1/2 onion
1 bay leaf
2 cloves

Instructions

Step 1 — Infuse the milk (10 min, optional)

Aromatize: For a more fragrant sauce, heat the milk over low heat with the half onion (studded with the cloves) and the bay leaf until almost boiling. Turn off, cover and let it steep for 10 minutes. Strain and discard the aromatics. Keep the milk warm.

Skipping this step is perfectly fine — the sauce is great with just the nutmeg. But warm milk makes it far easier to incorporate without lumps.

Step 2 — Make the roux (3 min)

Melt the butter: In a heavy-bottomed pan, melt the butter over medium-low heat without letting it brown.
Cook the flour: Add the flour all at once and whisk for 1 to 2 minutes, until it forms a smooth paste that smells like buttery biscuits. This cooks out the raw-flour taste — don't let it brown so the sauce stays white.

Step 3 — Add the milk (8 min)

Incorporate gradually: Over low heat, add the warm milk in a thin stream, whisking constantly after each addition until smooth before adding more. The first ladlefuls thicken fast; keep whisking to break up any lumps.
Cook and thicken: Once all the milk is in, raise to medium heat and cook, stirring constantly, for 3 to 5 minutes, until the sauce thickens and coats the back of a spoon.
Season: Off the heat, adjust the salt and pepper and finish with the nutmeg.

Tips

Lumps form when cold milk hits a hot roux all at once. Add warm milk gradually — or, if it has already gone lumpy, pass the sauce through a sieve or blitz it with a stick blender and it'll come back smooth.

The base ratio is easy to remember: equal parts butter and flour to ten times their weight in milk. Double the flour and butter for a thicker sauce (for croquettes); cut back for a pourable one
Turn it into a mornay sauce by stirring in 80g grated cheese (gruyère, parmesan or a mild melting cheese) off the heat until melted
Press plastic wrap directly onto the surface to stop a skin forming while it rests
The sauce thickens as it cools; to reuse, reheat gently with a splash of milk to loosen it