A generation ago, many Americans wouldn’t get near a piece of squid, much less an octopus. But now both of them have become relatively common fare. Squid and octopus are the two cephalopods (cephalopod means “head foot”) most often encountered in American markets. In Europe, and in fancy markets in the United States, you may find cuttlefish, which is like large squid. It has thicker, meatier flesh, but its flavor is much the same. Its one distinct advantage over squid is its ink sack, which contains about a tablespoon of smooth, very black paste, enough to impart a dramatic color to a stew, risotto, soup, or pasta dish.