Growing up we called this Misoyaki Butterfish, and it was something my Mom made on a regular basis. It seems that Nobu Matsuhisa, and a large contingent of popular chefs have made this into quite a popular dish. A few months ago someone requested my recipe, so here it is.
There are a few differences between my Mother's recipe and the Misoyaki I make nowadays. First, the Missus hated the grainy texture; my Mom's recipe called for just mixing several ingredients together. I've seen recipes where a Bain-Marie(double boiler for us...) is used to mix everything. But this didn't solve the problem of the excess alcohol flavor, so I've solved that problem by first boiling the sugar, mirin, and sake, this will ensure a smooth texture since the sugar is dissolved, and all the alcohol is burnt off. There is a another potential problem, miso should never, ever be boiled, this solved by just removing from heat before adding miso. My Mom used grated ginger in Her recipe, I've removed it from mine. But I've noticed that many Misoyaki recipes are much too sweet for my tastes, so I made a few adjustments. I've found that the addition of Aka ("Red" Miso) adds a bit of a salty flavor, and even some "depth" to the dish. One more note to "Nobu" fans out there...if you've had a problem with your miso glaze, it's because he uses a very high quality "Saikyo" Miso, I've found that the regular White Shiro Miso I use is not quite as sweet. In fact, when I did use Saikyo Miso, my recipe ended up tasting waaaaay too sweet! I just use a Mild White Miso, though I prefer the very mild Hawaiian Miso & Soy Company brand, I've found several others at Nijiya that do just fine.
Misoyaki Black Cod
Combine Mirin, Sake, and Sugar in a small pot. Bring to a simmer stirring constantly until sugar is dissolved. Simmer for 2-3 minutes, until all the alcohol burns off. Remove from heat, and add Soy sauce to stop boiling. Slowly add Miso mixing until sauce is creamy. Do Not ever boil miso.....When sauce is cooled marinate black cod completely coating the fish. Marinate for at least 2 days, but 3 days is best. If using a conventional oven, pre-heat at 450 and bake fish for 5-8 minutes. When fish is almost cooked broil for an additional 2-3 minutes until well caramelized.
If you are doing batches over time, divide miso sauce into 2 "batches", brush misoyaki over fish and wrap each in plastic wrap. When broiling or cooking brush on miso glaze as necessary.
The Missus's favorite way of cooking Her fish is to use the toaster oven, she bakes until almost cooked than toasts it.
Why no good photo...well as is the norm, the fish usually doesn't make it to "full-term", and I'll return from work smelling the remnants of Misoyaki on the Missus's breath. At least this time She took a photo as she removed the fish from the toaster oven....not the most artistic photo, but I guess it'll do! Here's the Misoyaki Black Cod eaten 2 days earlier than it should be.....
As you can tell, nothing is written in stone.....have fun with it.