Bok choy is a leafy green vegetable, but it has a much higher stalk-to-leaf ratio than spinach or Swiss chard. I’ve mostly seen it in Asian food. It’s a great substitute for cabbage in chow mein, and I use it in stir-fry. It’s a little steep in regular grocery stores, but the Asian markets have lower prices and more variety. My favorite is a thinner, shorter type that has a green stalk instead of the usual white.