I think I know what the sandwich is that you mentioned in your book. It is a Fukienese specialty. The bread is called Guang Bing. It is kind of like a bagel in shape only. folklore has it that this is what the Chinese troops ate when they were on the march. The hole in the middle allowed them to carry a bunch of them on a string around their neck.
The green stuff is mustard greens. They put the lid on the pot after they turn off the heat and they smother the greens in order to bring out the horseradishy taste. Folklore has it that the cook cookingthe mustard greens must have a scowl on his face in order to properly bring out the heat.
I love the stuff, I grew up on it. There used to be a pretty decent Fukiense place in Chinatown in NYC but that was almost 30 years ago, but I don't know if it is there anymore.
By the way, Fukienese food is pretty awesome. You have to try the Taro Mud. Is is just mashed taro cooked in lard with preserved fruits and sugar. Oh my goodness. That is the most sublime desert I have ever had.
Then there is the Fukienese soups and and fish balls. Yum!!!!!!