Pesto is a thick Italian sauce whose classic form is crushed basil with garlic, pine nuts, olive oil, and hard cheese (usually Parmesan). The name itself points to pounding: it was made in a mortar. In restaurants, “pesto” often means that green basil sauce on pasta, but cooks now stretch the word to other pounded sauces (sun-dried tomato pesto, for example). It is an everyday food word, not formal. In Taiwan a pasta shop’s 青醬 is usually this, or something close to it — though actually 青醬 can also mean any green sauce, so the menu word is a little looser than the Italian one.

青醬（義式羅勒醬）。菜單上的「青醬」有時只是綠色醬，不一定是真正的 pesto。