Tatsoi (Botanical name Brassica rapa) is a close relative of chinese cabbage and bok choi.  It has dark-green, spoon-shaped leaves, a subtle peppery flavor, and a crunchy texture.  Originally cultivated in Southern China, tat soi is a cool weather crop that is grown in the spring and fall in the Northeast.

Tat soi can be eaten raw, tossed into salads (you can chop larger leaves), or as a garnish on sandwiches.  It can also be cooked, and added to sautes, stir-fries, or soups.

Source: Just Food

Photo credit: sleepyneko on flickr via a Creative Commons license.