Cool, thanks for the tip! Just reading up now on growing mustard as a cover crop, sounds like something I should try.
I cook it like collard greens - smoked pork hock liquid (if not with some of the pork), onions, a touch of vinegar, served with hot sauce. Since I built my new house I haven't started a garden again, but once this summer is done (I'm in the Southern hemisphere) I'll at least make some space for these.