This is a very simple and delicious log-style sushi. Traditionally it is made using a square box to press the marinated fish onto the sushi rice and then it is cut into neat rectangles. At Masu we follow this approach but press the rice into the natural shape of the prawn tail.
Begin by removing and discarding the heads of the prawns. Carefully remove the tail shell to the last part of the tail section – you want to keep the last segment. With a small knife, butterfly the prawn by cutting from the base to the top, but don’t cut right through. Remove the vein and press the prawn out flat, into a nice even butterfly.
To make the marinade, combine the ponzu vineg