Kale or borecole is a form of cabbage (Brassica oleracea Acephala Group), green or purple, in which the central leaves do not form a head. It is considered to be closer to wild cabbage than most domesticated forms. The species Brassica oleracea contains a wide array of vegetables including broccoli, cauliflower, collard greens, and brussels sprouts. The cultivar group Acephala also includes spring greens and collard greens, which are extremely similar genetically.
Kale freezes well and actually tastes sweeter and more flavourful after being exposed to a frost.
Tender kale greens can provide an intense addition to salads, particularly when combined with other such strongly-flavoured ingredients as dry-roasted peanuts, tamari-roasted almonds, red pepper flakes, or an Asian-style dressing.
In the Netherlands it is very frequently used in the winter dish stamppot and seen as one of the country’s traditional dishes, called Boerenkool.
In Ireland kale is mixed with mashed potatoes to make the traditional dish colcannon. It is popular on Halloween when it is sometimes served with sausages. Small coins are sometimes hidden inside as prizes.
A traditional Portuguese soup, caldo verde, combines pureed potatoes, diced kale, olive oil, broth, and, generally, sliced cooked spicy sausage. Under the name of couve, kale is also popular in Brazil, in caldo verde, or as a vegetable dish, often cooked with carne seca (shredded dried beef). When chopped and stir-fried, couve accompanies Brazil’s national dish, feijoada.
In East Africa, it is an essential ingredient in making a stew for ugali, which is almost always eaten with kale. Kale is also eaten throughout southeastern Africa, where it is typically boiled with coconut milk and ground peanuts and is served with rice or boiled cornmeal.
A whole culture around kale has developed in north-western Germany around the towns of Bremen, Oldenburg and Hannover as well as in the State of Schleswig-Holstein. There, most social clubs of any kind will have a Grünkohlfahrt (“kale tour”) sometime between October and February, visiting a country inn to consume large quantities of boiled kale, Kassler, Mettwurst and schnapps. These tours are often combined with a game of Boßeln. Most communities in the area have a yearly kale festival which includes naming a “kale king” (or queen).
Curly kale is used in Denmark and Halland, Sweden, to make (grøn-)langkål, an obligatory dish on the julbord in the region, and is commonly served together with the Christmas ham (Sweden, Halland). The kale is used to make a stew of minced boiled kale, stock, cream, pepper and salt that is simmered together slowly for a few hours. In Scotland, kale provided such a base for a traditional diet that the word in dialect Scots is synonymous with food. To be “off one’s kail” is to feel too ill to eat.
In Montenegro collards, locally known as rashtan is a favorite vegetable. It is particularly popular in winter, cooked with smoked mutton (kastradina) and potatoes.
Kale is a very good source of iron, calcium, vitamin C, vitamin K and Carotenoids (which provide vitamin A). In Japan, kale juice (known as aojiru) is a popular dietary supplement.