Look for fish with bright eyes and glinting silvery sides.
If you’re a pescatarian locavore, you’re probably already familiar with butterfish. Not to be confused with escolar — which is also sometimes evasively called butterfish, or white tuna — the true butterfish are completely wholesome, with a flesh that’s fine textured, snowy white, and slightly sweet. Note that escolar, said to cause the runs due to its high waxy ester content, is a longer and darker fish, usually with stunted spines sticking out of its back. Another name for butterfish is sheepshead — presumably the same fish the Brooklyn neighborhood is named for.
Butterfish are small and delicious. There are any number of ways to prepare them, but they have to be cooked whole (after cleaning, of course), since the fillets would otherwise be too minuscule. Here are several recipes. The best part is the price: around $1.80 per pound for fish usually caught somewhere between Maryland and Canada, and recently, too.
Purple yams look normal from the outside, with a grayish brown skin, but once you cut into them …
The purple yam can be treated like any other yam — boiled, steamed, served by itself, or mashed with another vegetable. My favorite cooking method involves oiling them lightly and baking them around 300 degrees for 45 minutes to an hour, until the flesh is soft and the skin crisp and browned, even slightly charred in spots. The baking concentrates the color instead of dissipating it, the way boiling does. Eat it like a baked potato.