Rating: Excellent. This is now a classic in Japanese restaurants, and it is so simple and easy to make at home.
Status: Cooked a few times.
We followed the recipe for "Black Cod with Miso" by Nobu Matsuhisa published in "Food & Wine". It is a traditional Japanese dish, but Nobu made this dish famous and is probably the reason why this dish is so popular in so many Japanese restaurants in the United States today. 0.5 lbs was the right amount of black code for two people, since this type of fish is very oily and rich tasting. The fish needs to marinate for 2 to 3 days (we marinated ours for 2 days) so you need to plan ahead, but it is very easy and quick to cook.
Nobu's recipe sears the fish in a grill pan before baking it (we just seared ours in the same cast iron skillet that we used to cook the fish in the oven). If you want to oil your pan, then you should use a neutral vegetable oil (we used grapeseed oil). An alternative (which we didn't try) is to bake the fish, and then caramelize it using the broiler as Momofukufor2 does. Another alternative is to grill the fish--we successfully grilled our fish in a grill set to medium, flipping the fish once half way through cooking.
The first time I cooked this, I let my fish come to room temperature on the counter for about an hour before cooking (room temperature fish and meats tend to cook through more evenly). We cooked the fish for the full 10 minutes. Since it was also a thin fillet, this was slightly too much cooking time; since black cod is a very oily fish it was still moist but the fillet was falling apart; next time I cook a fillet would reduce the cooking time by a couple minutes. The second time, I left the fish in the refrigerator until just before cooking and it was also a thick 1 1/2 inch piece; 10 minutes was perfect. Also it didn't seem to matter whether you cook this fish directly out of the refrigerator since you are cooking it through and the oiliness gives you a bit of leeway, so I would probably just leave it in the fridge until I need it, since that is easiest.
The first fillet had its skin removed. The second fillet still had skin attached; since William likes to eat the skin we tried leaving it on. My recommendation is to remove the skin next time; the miso glaze can't penetrate the skin, so there wasn't enough of the sweet miso flavor on the skin side.
The recipe makes a lot of marinade--more than enough for two 1/2 pound fillets with lots of extra; you might want to consider only making half the marinade. The marinade keeps for 4 - 5 days, so after you make a fillet, you can marinate another.
The first time I made this, I served it with soba noodles in a soy-dashi broth. The second time, I served it with Japanese-style rice (Tamaki Gold, a short grain Californian rice), and egg tofu with enoki mushrooms.
You can also use this sauce on other types of fish. I have tried it on swordfish, and I have heard (though I haven't tried it myself) that it is good on salmon too. However, black cod is my favorite; I think the sweet miso glaze goes best with the rich tasting black cod.
Grilled Swordfish. This is 1.12 lbs of swordfish; since it is a larger piece of fish I used the full amount of marinade that the recipe makes. It was cooked on a grill (set to medium), flipping it over halfway through cooking. We cooked it about 20 minutes, but that was slightly too long.