To measure 2¼ cups uncooked Japanese short-grain white rice, overfill a US cup measure or a rice cooker cup with uncooked short-grain rice and level it off. Put the rice in a large bowl. Repeat until you have the amount of rice you need.

Rinse and wash the short-grain white rice and cook it with a rice cooker, pot over a stove, Instant Pot, or donabe.

While the rice is cooking, prepare the ingredients for the fillings.

For the Japanese Salted Salmon Filling: Place 1–2 fillet salmon on a baking sheet lined with aluminum foil or parchment paper. Sprinkle Diamond Crystal kosher salt on both sides. Broil or bake at 425ºF (218ºC) for 10–20 minutes. Break the cooked salmon into flakes and set aside.

For the Okaka Filling: Put 1 packet katsuobushi in a bowl and add 1 Tbsp soy sauce. Mix to combine.

For the Tuna Mayo Filling: Put 1 can albacore tuna in a bowl. Add 2 Tbsp Japanese Kewpie mayonnaise and ½ Tbsp soy sauce. Mix to combine.

For the Umeboshi Filling: Remove and discard the seed from 2 umeboshi and put the umeboshi flesh on a small plate.

For the Mentaiko Filling: Cut 2 sacs spicy salted pollock roe in half and squeeze out the roe from the sacs.

Gather all the ingredients to make the onigiri and a bowl filled with water for your hands.

Transfer the freshly cooked rice to a large bowl and let it cool slightly until it’s cool enough to handle.

Prepare another bowl filled with water. Soak the onigiri mold and lid in the water to moisten.

Fill the mold halfway with warm rice, add a spoonful of your filling of choice, fill the rest of the mold with more rice, sprinkle the top with more salt, cover with the lid, and push down firmly.

Remove the lid, flip the mold over, and push the button to release your onigiri onto a baking sheet.

If shaping by hand, wet your palms, apply salt, scoop a handful of rice, create a well in the center, add filling, cover with more rice, and mold into a triangle shape.

Wrap the onigiri with nori and enjoy warm or at room temperature.