To prepare the rice, strain it through a fine-mesh sieve with lots of cold water. Till the water flows clean, rub the rice grains between your fingers. By doing this, extra starch is eliminated, and the texture of the cooked rice is improved. Clearly drain the rice.
Then, combine the rice and water and cook them in a rice cooker as directed by the manufacturer. The best-textured sushi rice is guaranteed with this procedure. In the absence of a rice cooker, mix the rice and water in a medium saucepan—preferably one that is nonstick. In the end, bring the mixture to a boil before turning down the heat.
Cook the dish with the lid on for 16 to 18 minutes, or until all the water has been absorbed. Then, turn off the heat and use a rice paddle or a wooden spoon to gently fluff the rice.
After covering the pot with a fresh kitchen towel and a lid, leave it alone for ten minutes. Make the onigiri filling as the rice begins to slightly cool.
Creating the filling: After that, stir the albacore tuna, mayonnaise, spicy sauce, and rice vinegar together with a fork in a medium bowl until well blended. Add the scallions and stir.
Set up a medium bowl of room-temperature water and a small bowl of kosher salt for pinching while you assemble the onigiri. Start putting together the onigiri by hand as soon as the sushi rice is cold enough to handle.
Put your hands in the water basin to moisten them. This stops the rice from clinging to your hands while you're moulding it. Rub your palms together after lightly sprinkling them with kosher salt.
Then, using one palm, gently massage about half a cup of sushi rice into a thick, oblong form. Put a tablespoon of the tuna filling in the centre of the rice and press it together with your fingertips. Using a pinch or two more rice, if necessary, cover the filling with the rice.
Use the palms of one hand and the fingers of the other to gently mould the rice ball into a broad triangular shape. As you move, rotate the rice ball. However, try to avoid packing the rice too tightly; it should hold together well.
Sprinkle black sesame seeds all over the onigiri's outside. After that, wrap each onigiri in a sheet of nori and top each with a further tiny spoonful of tuna filling.
Finally, serve right away and take joy!