If I remember correctly, it is Bok Choy flower stalks, with the leaves and flowers cut off.

Could it be misspelt? In case it is Choy Sum, which in Cantonese means "vegetable heart", it very yummy and can be stir fried with sesame oil, garlic & shrimps ~ my lazy quick way.
Cut stems & leaves into 2" lengths; heat sesame oil; put in diced garlic; stir fry till fragant; put in shelled medium size shrimps, raise heat, stir fry +- 1min till slightly pink; remove shimps, throw in stems only + a tbsp of water, cook 1 min then add leaves and shrimps and stir fry till leaves darken & shrimps fully cooked. Add some pepper & a dash of soy sauce.
Above goes well with egg-congee or white jasmine rice.
See: http://www.recipetips.com/glossary-term/t--36228/choy-sum.asp sorry, don't know how to create a link here.

Thank you both for responding to my question. Yes, it might very well be misspelled Choy Sum. And thank you for the recipe. The green leaves had been removed before I bought it, but I will try it in a stir fry anyway. I will also google Choy Sum to see what other information I can find. Half of the fun in any hobby is learning new things.

Sounds very odd to be choy sum to be sold with leaves off. Easy to verify if it is or isnt if you had pictures of it.

Not that it's against the rules but in cantonese cooking, as far as I'm aware, choy sum usually isnt stir fried with garlic as oil&salt is enough seasoning

Hello, I am currently traveling in China. At a resturant today I had the pleasure of eating a dish with Choy Sum. The vegetable was prepared in a dish under a bed of noodles and thinly sliced beef. The vegetable was prepared similar to steamed broccoli but had a unmistakeable taste and texture of asparagus. I knew it wasn't asparagus by the same way others in this article have described it. However, if you had your eyes closed while eating Chow Sum, you would think it was asparagus. It was so tasteful I made the waiter write it down for me.

If you wish to grow it, Kitazawa offers seeds in the USA. Evergreen Seeds offers even more variety.

Here is a link that might be useful: Choy sum