An oxtail is exactly what it sounds like: the tail of an ox. They are officially classified as offal, along with an assortment of organ meats, and like other offal, it has a long and illustrious culinary history. Oxtails can be purchased at boutique butchers and sometimes at a butcher's counter in a large market, depending on the regional taste for the meat. Once purchased, it may be used immediately or frozen for future use.
To prepare oxtails, butchers remove the tail of a cow while it is butchered and skin it. The tail is typically cut into segments, making it easier to handle. It is extremely bony and also very muscular, and it requires special care in the kitchen. The best way to use oxtail is as the base for a stew, soup, or beef stock, as it benefits from long gentle braising. Oxtail can also make a soup taste a bit gelatinous, as it releases a great deal of collagen during the cooking process.
The terminology surrounding the oxtail is a bit complex. Traditionally, it came from oxen, neutered adult cattle used as dray animals. Over time, however, oxtails have been harvested from any sort of cattle, including steers and veal cows. Some people feel that traditional oxtail has the most flavor, because the longer a cow lives, the more muscle develops in the tail, and as a result the flavor tends to be stronger and more complex.
As with other offal, the taste for oxtail probably arose from necessity. Many cultures have a long tradition of trying to use every part of every animal butchered, with the offal typically ending up in the pots of the lower classes, since they could not afford the more prized cuts of meat from the animal. Innovative cooks developed all sorts of interesting ways to use offal, and while it was once a lower class food, offal is now included on the recipes of many gourmet restaurants, especially those which offer traditional European cuisine.
The classic use of this meat is in oxtail soup, a venerable English classic. Oxtail also crops up in a lot of Caribbean food, especially in Jamaica, where a soup with butter beans is extremely popular. The well developed, rich flavor of a slowly braised oxtail can be quite memorable and very strong, and it is often included in the packaged beef bouillon sold at many markets. When oxtail stock is made at home, it can be frozen for future use if the cook thinks he or she won't be able to use it up.