Béchamel might be the most versatile mother sauce — that class of sauces that are the backbone of classic French cooking — of all time. Made with milk, butter, and flour, it can become a gravy or a binder for casseroles, cheese sauces, and soufflés. And while it is arguably the easiest mother sauce to master, it is often the most maligned, being hastily made and suffering lumpiness as a result.
You can't cover those mistakes up with all the cheese in the world, so let's get it right the first time. By just avoiding a few missteps and following these five simple tips, you can make silky-smooth béchamel every time.
1. Using the wrong ratio.
I admit it — I often eyeball my roux by throwing a dab of butter and a few spoonfuls of flour in the pan. Mostly it works out fine, but guesstimating often leaves me with a too-thick or too-thin sauce.
Come correct: The basic ratio for a classic béchamel is 2 ounces of fat (butter, ghee, coconut oil) to 3 ounces of all-purpose flour for the roux. This ratio of roux will thicken up to a quart of milk, but you can use less milk for a thicker sauce.
2. Not cooking your roux the correct length of time.
Roux is deceptively tricky to cook. Once it's reached the brown stage, it's lost some of its thickening ability and you will need more of it to thicken a sauce. On the other hand, for a béchamel, we need a white roux that's cooked just long enough so it doesn't taste like raw flour.
Try this: Pay close attention to the cook times given on a recipe as a place to start, then rely on sight and taste for the best result. Cook the roux until it appears dry and smells nutty, at least five minutes. You can also give it a taste around that time. It should be free of any "cereal" or raw flour flavor.
3. Using cold milk.
Okay, you can make béchamel with cold milk, but it's going to make a bigger mess and take longer to cook. Cold milk plus hot roux equals more spurting and splattering than frying chicken (and even more cleanup!).
Warm it up, Kriss! Warm your milk for one to two minutes in the microwave. A glass measuring cup with a spout is ideal for warming and pouring.
4. Adding all the milk at once.
Adding all the milk to your roux at once is the fastest route to Lump City. The roux will be sort of "shocked" into clumping by the milk (this is especially true of cold milk), and you'll have a hell of a time whisking those lumps out.
Try this instead: Add about a quarter of the warm milk and whisk vigorously to loosen the roux up and knock out any lumps before slowly adding the remaining milk.
5. Not cooking it long enough.
You add the milk and it sort of simmered, so the sauce is done, right? I mean, it looks thickish in the pan. Not so fast! Béchamel requires more than just a simmer and some steady whisking before it's reached optimal thickness.
Know your béchamel is done: A properly thickened roux should "coat the back of the spoon," which means dip your spoon into the béchamel and then draw a finger through the coated spoon. Does the sauce wipe clean, leaving an open space? Then your béchamel is done and ready to add seasoning or cheese to.