- 3 cups (525g) cooked short-grain white rice (see note)
- 1/4 cup (60ml) soy sauce, plus more for serving
Wet your hands and divide rice into 4 equal-sized balls, approximately 2/3 cup each. Working with one ball at a time, squeeze and compress rice ball between your cupped palms to form it into a triangular shape. Set onigiri on a rimmed baking sheet and brush evenly all over with soy sauce. Repeat with remaining rice balls. Onigiri can be made in advance, covered with plastic wrap, and held at room temperature for up to 2 hours.
Light one chimney full of charcoal. When all the charcoal is lit and covered with gray ash, pour out and spread the coals evenly over half of the coal grate. Set cooking grate in place, cover grill and allow to preheat for 5 minutes. Clean and oil the grilling grate. If using a gas grill, preheat half the grill to high.
Add onigiri to cool side of grill and cook until the bottom side is browned, about 10 minutes. Using a spatula, carefully flip onigiri. Continue to cook until browned on the second side, about 10 minutes. Transfer to a serving platter and serve immediately with extra soy sauce alongside for dipping.
If you desire, you can use 2 cups cooked white rice and 1 cup cooked brown rice.