Kasu-Marinated Butterfish

No arm-twisting was required to convince us to try this different take on the Miso Butterfish we love so much — Butterfish marinated with Kasu, or sake lees. Happily, butterfish (a.k.a. sablefish or black cod) is a “Best” (from Alaska) or “Good” (from U.S. West Coast) choice on the Seafood Watch list. (Read more about choosing safe fish and shellfish for Hawaii, the US, and around the world.)

I’ve had kasu on my list of things to try for well over a year now, but with no luck finding it in the shops. A month or so ago, I spotted a new package on the top shelf of the Japanese refrigerated goods section at DQ (not the ice cream place, the former Daiei). I recognized the brand symbol on the cover as a sake brand, so that bode well. Sure enough, it contained sheets of sake lees. Yes, sheets — flat, compressed and heavenly-scented sheets. Not what I was expecting either — I had been looking for a paste-like product resembling packaged miso.

As soon as I could get my hands on a few butterfish fillets, we’d be set. The store I was in does not usually carry fresh butterfish so I made a mental note to look in Chinatown on our next visit. But when I wandered over to the fresh fish displays, there they were — butterfish steaks! And they were on sale that week. It was definitely a sign. Fillets would have been nice, but butterfish does not have many small pins or bones, so I left the steaks whole.

What exactly are sake lees? “Lees” is a nice word for the silty precipitate of dead yeast — and, in the case of sake, rice — that settles out from wine in the production process. It sounds much more palatable than “dregs,” doesn’t it? Sake lees, or kasu, have an incredibly intoxicating aroma. It is easy to see why sake vintners would be loath to simply discard the fragrant paste. Besides its use as a culinary ingredient, kasu can be further commercially processed to make a distilled liquor and a vinegar.

We have now tried both the marinated fish and a heady soup in which kasu was the star ingredient. Both were delicious and thoroughly addictive. (We’ll share more about the soup during soup season.) You can also try your hand at making pickled vegetables with kasu at home, but the most intriguing home use for kasu I found is as a moisturizing face masque! It is supposed to leave your skin baby-soft. And delicious smelling, too, no doubt! Kasu keeps for a long time, so buy it when you see it and tuck it away in the fridge until you need it.

This particular recipe requires long planning — 10 days of marination. There are a slew of recipes with much shorter marinating times, but most of them also include miso paste, sake or mirin, shoyu and other ingredients. I wanted to let the pure kasu flavor through so I devised this one after much reading. If you’d like a more subtle kasu flavor, I’ve had this recipe from the Honolulu Star-Bulletin bookmarked for months to try in future.

You can cook this after 4 days, but patience will be rewarded (here’s looking at you, Italy).

(inspired by an artice on esake.com)
1 TBL. sea salt
1/2 cup kasu paste, about 2 sheets
3 TBL. raw sugar
1/3 cup water
2 butterfish steaks or fillets with skin on, about 6-8oz. each

Combine kasu, salt, sugar and water, and stir to make a thick paste. Place half of paste in the bottom of a glass or other non-reactive pan.

Wash and pat dry the butterfish, and place on the kasu mixture. Cover fish with remaining kasu mixture. Cover tightly and put away in a corner of the fridge for 10 days.

When ready to cook, remove fish from refrigerator and bring to room temperature. Remove fish from kasu, and with a paper towel, gently wipe away most of the paste.

Pre-heat skillet over medium heat. Add 2 TBL. oil to pan. Season fish with salt (I used alaea salt, that’s the pink grains you can see past the water drop on my lens), then add to skillet, salted side down. Season the second side of the fish. Cook, uncovered, for 4-5 minutes — fillets will cook quicker than steaks. Turn over and cook another 5-6 minutes, or until fish is cooked through (will flake with a fork).

Serve with rice, pickled ginger, and flash-cooked greens dressed with sesame or ponzu dressing.