How to Make It
Heat the broiler or light the grill. If broiling, line a broiler pan or baking sheet with aluminum foil and lightly oil the foil.
In a medium stainless-steel saucepan, bring the soy sauce, mirin, and sugar to a boil, stirring. Reduce the heat and simmer, stirring occasionally, until thickened and reduced to 2/3 cup, about 10 minutes.
If broiling, put the salmon in the prepared pan. Brush the salmon with the soy-sauce mixture. Broil or grill until well browned, about 2 minutes. Turn and brush with more of the soy-sauce mixture. Continue cooking until the fish is browned and just barely done (the fish should still be translucent in the center), about 3 minutes longer. Brush with the remaining soy-sauce mixture and serve.
Fish Alternatives If you can find sablefish—a rich, succulent fish also called black cod, though it's very different from regular cod—by all means use it. Other alternatives are bluefish or mackerel fillets, but don't turn them during cooking or they may fall apart.
In Place of Mirin: This is one case where the substitute really is just as good as the original ingredient. In fact, in our taste tests we could barely tell the difference between this recipe prepared with mirin (sweet Asian cooking wine) and with sweet sherry. You can also use six tablespoons dry sherry and add an additional three tablespoons sugar.