Onigiri, or Japanese rice balls, are basically steamed rice hand-pressed into triangles (or other shapes) with or without filling and wrapped with seaweed. They are a staple to-go lunch or snack ubiquitously sold at Japanese convenient stores, supermarkets, airport, cafes, etc. and also made at home. Tuna Mayo Onigiri is one of the more popular flavours. It is simple, delicious and inexpensive to make at home using canned tuna fish. Since onigiri is a rice-forward food, make sure to use the right rice for it. Japanese short grain rice (sometimes labelled “sushi rice”) is chewy and slightly sticky – perfect for onigiri. Other rice types will not stick properly, causing the onigiri to fall apart.
Related: A Tamago Sando is the Japanese Twist on Egg Salad You Need
Cook rice: Wash and rinse rice grains until water runs clearer but does not need to be fully transparent. Drain in fine mesh colander at least 15 minutes. Place rice in a pot. Add 1 cup of water. If you have time, it’s highly recommended to soak rice in the measured water before cooking at least 10 to 30 minutes. After soaking, set pot over high heat. Cover with lid and cook until water is boiling and steam is escaping (usually 5 minutes) at which point, without lifting lid, turn heat all the way down to lowest and continue to cook 20 minutes. Fluff with rice paddle and allow to cool enough to touch with your hands – but still warm – for forming the onigiri.
Prepare mayo tuna filling: place tuna into small bowl and mash with a fork until pieces are broken down and the consistency is somewhat pasty. Add mayonnaise and soy sauce. Mix well. Divide into 5 equal portions (about 1 tablespoon each), reserving a little bit for topping the onigiri.
Assembly: Dampen both hands with water. Rub a pinch of salt between palms – this salt will season the rice as your form the onigiri. Scoop ½ cup of rice onto one palm. Use fingertips to create a divot in the middle and spoon 1 tablespoon of tuna filling into it. Push rice over to fully cover filling. To form triangular sides, place rice ball firmly in the crook of one hand. Cup other hand into a “v” and gently but firmly push on the rice to form a triangular corner. Rotate and repeat for the other two corners. Once you’re happy with the shape, wrap a piece of nori (shiny side facing out) around the bottom and fold up towards the middle. The seaweed will easily adhere to the rice.
Optional garnish: press furikake, aonori seaweed flakes or toasted sesame seeds onto the other two edges for garnish.
Dot reserved tuna filling on the top. Onigiri are best eaten fresh, warm or at room temperature. If making in advance, you may wish to keep the nori separate to prevent it from getting soggy as it absorbs moisture from the rice – wrap onigiri in cling wrap without the nori strip and attach nori strip just before eating.