Its Chinese name is "莴笋 wosun."

Remove the leaves from the stem (you can use these in salads, or cook/wilt them down and use in stir fries or soups as well).

For this dish, you can prepare any type of stir fry you like - any protein, sauce, other veggies, etc. 

For my favorite stir fry recipe, check out this blog post, and substitute the celtuce stems for broccoli (or add them in addition to broccoli).

To prepare and stir-fry celtuce stem: Get a pot of water boiling, to blanch the stem pieces, while you cut them up. Peel the outer skin from the stem, and slice the stem into long, thin strips. (Or any other shape you prefer - thin coins, diced, etc). Dunk the stem strips in boiling water for about one minute. Add the blanched strips to your stir-fry for just a couple of minutes, or until they reach your desired softness. That's all there is to it!

Mix things up by using different stir fry sauces.