Pat the fish fillets dry with a paper towel. Remove the fish skin with a very sharp knife or have it removed at the market. Brush the fillets with the soy sauce and place on a wire rack (skin side down) over a sheet pan and refrigerate for 30 minutes. Preheat the oven to 425°F.
2 Black Cod fillets, 2 Tablespoons soy sauce (low sodium)
For the sauce, add both types of peppercorns to a dry saucepan over medium heat. Once the peppercorns become quite fragrant (a couple of minutes), reduce the heat to low and add the shallots. They may stick to the pan at first, but that is fine. Add the sake and stir. Next add the miso paste, lemon juice and black sweet soy sauce and whisk until fully incorporated. Turn the heat back up to medium and cook for 3 minutes. Strain the sauce and return to the saucepan without any solids.
10 Sezchuan peppercorns, 10 Black peppercorns. whole, 1 medium shallot, ¾ cup sake, 1 Tablespoon white miso paste, Juice of ½ of a medium lemon, ½ teaspoon sweet black soy sauce
In an oven-safe nonstick skillet over medium heat, add the olive oil and then add the fish that has been brushed with soy sauce and has rested in the refrigerator for 30 minutes. Cook for about 4 minutes with the flattest side down. Then put the fish in the preheated oven for 6-10 minutes depending on how thick your fillets are. The internal temperature should be 145°F. Once the fish is done, remove to a plate and loosely cover with aluminum foil to rest while you finish the sauce.
1 Tablespoon olive oil
While the fish is cooking, reduce the sauce over medium low to low heat. It will become thicker (from the miso paste) and the sake will cook down. Once the fish is done, remove the reduced sauce from the heat and whisk in the cold butter, one piece at a time. Serve the black cod with some sauce and garnish with chives. Serve with your favorite side dishes.
4 Tablespoons unsalted butter - cold and diced