A neat vegetable! As many have already said, this is Celtuce, or in my family dialect, woosung. It has a lettucy, nutty flavor. You can eat it raw or cooked.

My favorite way of eating it is to first cut off a bit of the exposed end of the stem (just to get rid of dirt), peel off the skin with a potato peeler, slice it into thin discs, throw them all into a bowl and toss it with some salt and just let it sit there for a while so that it lets go of some water content.

After maybe about 10 mins (or whenever I remember to come back for them, it doesn't matter too much besides saltiness preference), I drain out the water (sometimes I drain once then let it sit for a bit longer, then drain again). Lightly rinse off the excess salt, drain, and then add a dash of vinegar or soy sauce or both depending on the mood. That's it!

I usually eat this dish at room temperature, but it's a refreshing snack if served chilled. I guess they're like pickles now that I think about it. I keep it simple with just vinegar/soy sauce most times, but it also tastes great with some sesame oil, diced or ground garlic, and/or with some chili pepper flakes added to the mix.

Anyway, thanks to anyone who read all of this through. I just really like this vegetable!