Wash kale well by dunking it in a bowl of tepid water several times and then rinsing under cold running water. Small kale leaves can be used whole. The larger leaves should be stripped or cut from the center rib. The rib can be chopped into small pieces and cooked with the leaf or discarded. To shred the leaves, place them in a pile, roll up, and then thinly slice them.
Baby kale can be used raw mixed with other greens in salads. Mature kale must be cooked, as it is too tough to consume raw. It can be steamed, but tastes best when boiled or simmered in vegetable broth.
Kale can also be added to soups and stews. It is especially good in soups that contain potatoes, barley, or beans. Kale with white beans and sausage is a traditional Portuguese soup. Good ways to flavor kale are to add any of the following: garlic, olive oil, fresh lemon juice, toasted sesame oil, cinnamon, caraway seeds, currants, or toasted pine nuts.
Traditional ways to prepare kale call for long cooking—about 40 minutes—until it is very soft. However, kale can also be boiled quickly, about 5 to 8 minutes, until it is just slightly crunchy.
Boil the kale first for about 5 minutes to enhance its flavor. Then sauté in oil with onions and garlic for about five minutes.
Place the kale, with just the water clinging to its leaves, in a covered microwave-safe dish. Cook on high for 7 to 10 minutes, stirring after 4 minutes. Let stand, covered for 3 minutes before serving.