Sauces based on milk rather than stock are of course much easier to make, and more forgiving; because they’re already milky, the cook doesn’t have to worry about long simmering to clarify them. The classic starch-thickened milk sauce is béchamel, whose only other ingredients are seasonings and the butter in which the starch is precooked for a couple of minutes. Once the milk has been added to the roux, the sauce is simmered for 30–60 minutes with occasional skimming of the skin of milk and flour proteins that forms at the surface. Starch is more effective at thickening milk than it is meat stocks, apparently because it bonds both to the milk proteins and the fat globules and so recruits these weighty ingredients into its flow-slowing network. Thanks to its pleasant but neutral flavor, béchamel is a versatile sauce that can be imbued with many flavors and served with many main ingredients. It’s also made in several thicknesses for a variety of purposes. Thick preparations (6% flour by weight) serve as the base for soufflés, somewhat thinner ones as a moistening and enrichment for gratins.