To make Soy-Mirin Marinated Black Cod, in large pan, combine soy sauce, mirin, green onions, lime juice and ginger. Add black cod; turn to coat well. Marinate at least 1 hour.
To make Tosazu Broth, in non-reactive saucepan, bring dashi, soy sauce, vinegar and sugar to a simmer. Add bonito flakes; bring to a simmer. Immediately remove from heat; strain through cheesecloth-lined strainer. (Yield: 10 cups)
For each serving, to order, place 1 fillet Marinated Black Cod on sizzle platter; roast in wood-burning or gas oven at 600°F for 5 minutes or just until fish can be flaked with a fork. Transfer to shallow serving bowl. While fish is cooking, heat 1 mushroom in 6 tablespoons Tosazu Broth. Pour broth and mushrooms over fish. Garnish with 1 tablespoon green onions, 1 tablespoon micro arugula and 1/8 teaspoon lemon zest.
Recipe by Chef Paul Muller, Taneko Japanese Tavern