Rub both sides of the fish fillets with sugar, place in a shallow tray, cover with plastic wrap and refrigerate for 2 hours.
Rinse off both sides of the fillets under running water, and pat dry with paper towels. Rub salt into both sides, place in a shallow tray, cover with plastic wrap and refrigerate for 3 hours.
Rinse off both sides of the fillets under running water, and pat dry with paper towels.
Pour the vinegar into the shallow tray with the fillets placed skin side down. Place a paper towel on top of the fish so that they are immersed in the vinegar. Cover with plastic wrap and refrigerate for 4 hours.
Peel off the skin with your fingers.
Remove any remaining bones with fish bone tweezers.
Wipe off the vinegar well with paper towels.
Wrap the fillets in plastic wrap, and refrigerate for half a day.
Mix sushi vinegar into freshly cooked hot rice using a rice paddle. Fan to cool it down. (I have added some pickled ginger and toasted sesame seeds to the rice here).
Slice off a bit of the fish in the middle that is thicker than the rest, and stick it on to the tail end to even out the thickness.
Line a makisu (sushi rolling mat) with plastic wrap, and place a mackerel fillet on it skin side down. Cover evenly with sushi rice, and roll with the mat.
Press down with your hands to even out the shape. Secure the mat with elastic bands, leave for 2 to 3 hours and it's done.
Story Behind this Recipe
I love saba sushi, but it's hard to find one in stores that's made just to my taste, so I make my own. For the sugar marinating step, I've used Chef Hiromitsu Nozaki's method as reference.
Adjust the time you marinate the fish in salt and vinegar to taste. After forming the sushi, if you refrigerate it, the rice will harden. If you wrap the sushi in a towel and put it in the vegetable compartment (the warmest part of the refrigerator) or similar, you can prevent the rice from becoming too hard.