I've finally gotten enough supercorns to make a supercorn seed. I planted it and grew some supercorn. Eventually I should be able to have a whole crop of supercorn.
Eating. Two supercorns is more or less the equivalent of the best cooked foods currently in the game at refilling hunger, without having to actually prepare them in any way.
I did hear tell of a poi called Carls Seeds where you could get some. I have seen it in one of my games (in Navezgane) but i didn't go in at that time so I don't know for sure.