Use the measuring cup and water lines on the cooker bowl to cook 1 rice cooker cup of rice.

If you're doing it on the stove, wash the rice in a few changes of water until it runs mostly clear. Drain it then add to a tall pot with water. Cover, bring to boil over high heat, then reduce and simmer for 13 minutes. Let it steam for another 10-15 minutes.

Once it's done steaming, pour the soy sauce evenly over the rice and use a folding motion with a spatula to distribute.

Level off the rice mixture and divide it into thirds. Shape into yaki onigiri using hands or an onigiri mold.

Dust each onigiri with potato starch, flipping to coat both sides.

Heat oil in a non-stick frying pan over medium-low heat. Add onigiri to fry until golden brown on one side, about 7-10 minutes.

Flip and add more oil to fry the other side until crisp. Melt cultured unsalted butter on each side and roll on its edges.

Serve wrapped in Shiso leaves or Nori sheets.