Just made black cod and man was it worth it. I've eaten Black Cod in a few places, best of which was Tsunami in Clapham. The recipe I followed called for the following marinade:
125ml oz sake
225g white miso paste (available in some Asian grocers and supermarkets)
Soak those bad boys overnight and you have a dark sweet fish that needs a few minutes under a hot grill, followed by 5 mins in a hot over. I had to substitute vermouth for sake, as the missus baulked at the price of the sake in Sainsburys! But she liked it so much, I think it'll be in the cupboard next week. Either that, or I'll do the shopping this weekend. Whatever - it still tasted great. Worth prepping on a Sunday for a Monday bonus.