Amazingly simple; amazingly good.
The cookbook I got this from says it's good over green beans, also asparagus and broccoli, but also pasta or rice or whatever. I'm going to put it on sandwiches. It's quite salty, though because of the miso. But fucking excellent. You have to use good miso -- go to the nearest Chinatown, go into any grocery (I went to the huge underground one on 11th and Race), and buy the kind of miso that comes in a bag that has no English on it.