Tatsoi – Before we start: you’ve almost certainly eaten tatsoi before. The mild, mustardy leaves often show up in mixed salad greens, so — surprise! — you’re probably already acquainted. What’s so great about this green? Once you track it down, (aliases include tat soy, tat soi, broadbeak mustard, spoon mustard, spinach mustard, and rosette bok choy), it’ll quickly become one of the most versatile green vegetables you know.