Marinated Halibut

Ingredients

• 1 pound skinless, boneless halibut
• 1 bunch mitsuba, finely chopped
• 1/3 cup daikon radish, grated
• 6 scallions, white and light green parts, finely minced
• Ponzu sauce, for dipping (recipe follows)
• Juice of 4 lemons
• 1/3 cup plus 2 tablespoons rice vinegar
• 1 cup dark soy sauce
• 2 tablespoons tamari sauce
• 3 tablespoons mirin
• 1/3 ounce dried bonito flakes
• 2 inch square giant kelp (konbu)