Hamachi is, of course, farm-raised yellowtail from Japan. It is almost buttery in texture, with a lovely bold flavor. This is my wife’s favorite roll. You can replace the hamachi with any type of oily fish.
In a small bowl, make the vinegar water for dipping your hands by combining the water and 2 to 3 tablespoons (30 to 45 ml) of rice vinegar.
In a small bowl, combine the hamachi and scallions.
Open a makisu (bamboo rolling mat) and place the nori sheet, textured-side up, on it. With wet hands, spread the sushi rice over three-fourths of the nori sheet,