No menu, or limited hours eateries?
I'm looking for interesting food - where restaurants that don't have a menu and you eat what the chefs have made that day. (and the food is great). Or popup restaurants. Or someone's "hobby" restaurant. I hear things "oh, that Indian place in Santa Clara, where you get whatever they made for that night" or "the Italian place that serves family style in Sunnyvale but is only open a few days a week", but haven't had much luck tracking them down.
I'm thinking chowhounds might collectively know a bunch of places, and I'm getting hungry, so spill...
Guest Chef in Oakland
Mr. Pollo listed above is exactly what you're looking for. The chef is also doing a pop up a few doors down (search, it was recently alluded to)
Some of these might work, if only because they're difficult to get to if you don't work in SF: