Cut fish into serving pieces
Put fish in a plastic bag and marinate for 12 hours in Saikyo Miso (see recipe below), turning every now and then.
Drain fish, reserving 3 Tablespoons of the marinade for the Dashi sauce (recipe below).
Broil fish for 2 to 3 minutes to caramelize the flesh. Turn, skin side up, and broil for another 2 to 3 minutes. Serve with Dashi sauce.