Have all ingredients at room temperature, about 70 degrees F. Preheat the oven to 350°F (325°F if you use a glass baking pan). Grease a 9-inch square or round pan or an 11 x 7-inch baking pan....
One of the aspects of cooking that I like the best is the challenge of using everything. Much is made of chefs who turn radish tops into elegant appetizers or make pickles out of chard stems. But really, any chef worth her salt is always looking for ways to prevent food waste. Any food that comes in the door was paid for. Any food that is thrown away is like throwing cash into the garbage. Restaurants are notoriously difficult to keep afloat because the profit margin is razor thin. Successful chefs are successful in part because they fight food waste tooth and nail.
But you don't start out in the kitchen thinking about food waste. You start out thinking about how to boil an egg or truss a chicken. Then, after the dust has settled and you come into your own, cooking becomes more about the process. And you might notice that during this process, things are thrown out. You become more interested in using those challenging bits and pieces that might not look like much on their own. Leftover pickle brine. Spent vanilla beans. Potato peels. Every ingredient can have a "long tail" if you remain open to exploring its possibilities.
In many cuisines, leftovers are valued and even elevated. In France, stale bread becomes pain perdu--French toast. In Eastern Europe and Jewish communities around the world, rendered chicken fat is used to fry latkes, flavor matzoh balls, and make chopped liver. Speaking of offal, ours is one of the few cuisines that treats odd bits like second class citizens. It's not just about being frugal. It's about not missing out on the exquisite, often heightened, flavors and textures of those odds and ends. For me and for many other enthusiastic home cooks, it's also about the feeling of satisfaction you get from using everything.
When I first heard about cooking with sake lees or kasu, a byproduct of sake production, I was immediately intrigued. My introduction to kasu was a black cod fillet that had been marinated and broiled to a deep golden color. The interior flesh of the fish was rich and soft, the skin was crisp, and the golden outside layer was sweet and salty. Black cod, also called sablefish, is a luxuriously fatty fish that stands up well to being broiled. While a leaner fish might also benefit from a kasu marinade, the only way to achieve the exquisite balance of rich, soft fish and a deeply caramelized exterior is to use a very fatty fish. If you can't find black cod, you can substitute king salmon. Most other fish will dry out before it achieves a good golden crust.
I think that one of the things I find so appealing about this dish is that it is so elegant. From using a byproduct to flavor the fish to using a quick cooking method to achieve a flavorful crust, everything about kasuzuke is simple, streamlined, and utterly delicious. I confess to not knowing much about Japanese cooking, but based on what I do know, the Japanese have a knack for this sort of dish. Completely understated and ingredient-driven, but so delicious and lovely that it makes sparks fly inside your mouth. This is one of those recipes I'll keep in my back pocket whenever I need to impress a dinner guest.
We were able to find sake lees very easily in the seafood department of our local Japanese supermarket. Thanks to increased enthusiasm for sake, American sake breweries—once exclusive to California and Oregon—can now be found in Washington state, Colorado, Minnesota, North Carolina, Texas, and Maine. If you live near a sake brewery, you may be able to find kasu at quite a bargain. If you can't find kasu, we have included a recipe for a miso-based marinade in the headnote that will help you achieve a similar result.
The sake lees (kasu) make a big difference in this recipe. You can find it at Japanese grocery stores and online. If you can’t find the sake lees or do not have the time to hunt it down, substitute for the marinade below 1 tablespoon sugar, 1 tablespoon soy sauce, and 1/4 cup each: sake (preferably unfiltered), white miso, and mirin. A nice fatty salmon fillet can fill in for black cod if that’s too hard to find.
Place in a gallon-size zip-top bag:
1 1/2 to 2 pounds black cod fillet, cut into 4 pieces
Mix in a bowl:
1/2 cup sake lees (sake kasu)
1/4 cup mirin
1/4 cup water
2 tablespoons brown sugar
2 tablespoons white miso
1 tablespoon soy sauce
Scrape the marinade into the bag, carefully squeeze the air out, and seal it. Shake the bag until the fillets are coated with the marinade. Put on a tray or large plate and marinate in the refrigerator for at least 1 hour and up to 2 days.
Put the rack of your oven as close to the top as it will go and preheat the broiler for 10 minutes. Meanwhile, drain the marinade, remove the fillets from the bag, and wipe dry with a paper towel. Put the fillets skin side down on a sturdy rimmed baking sheet lined with aluminum foil. Broil until the surface is nicely browned and the fish begins to flake when prodded with a fork, about 5 to 6 minutes for 1-inch-thick fillets.
Remove from the oven. The broiling causes any pin bones to protrude from the fillets. Remove them (pliers or fish tweezers are good for this) and serve the fillets with:
Rice (mixed with a little rice vinegar if you want)
Sprouts or tender greens