You can use the stalks in place of celery in recipes (I use it in soups for that quite often). It is good roasted and you can even make rolls with them (like cabbage rolls) filled with whatever (tofu, grains, veggies). I love it (and I'm not a big chinese food eater) and it's also pretty cheap around here. I'm not a vegetarian but thought I'd suggest what I like to do with it anyway.
I sautee some garlic and grated ginger in a little oil, toss in chopped bok choy for just 30 seconds, sprinkle with sesame oil and sometimes put a little tamari or soy sauce on it. Sometimes I mix scallions and mushrooms in as well. Yummy.
Stir-fry in a small amount of sesame oil mixed with sunflower oil (or another bland oil that can be used for frying), chopped ginger and some almonds. Dress with soy sauce and eat with rice or similar.
Put into miso soup along with other traditional ingredients, such as tofu, carrots, spring onions.
Eat raw in salad - nibble a bit and see if you fancy it this way.