Japanese rice balls, called onigiri or omusubi, are compact triangles of cooked rice stuffed with a tasty filling and often wrapped in a sheet of toasted nori. Cute, portable and healthy, they’re one of our favorite ways to eat lunch on the go.

In Japan, onigiri can be purchased at any convenience store or supermarket, but they’re also often a homemade treat tucked into lunch boxes. Hot rice is salted, shaped into a ball or triangle, and usually stuffed with a bit of fish, meat or pickled plum (umeboshi). The rice can also be mixed with a flavorful add-in like furikake and left unstuffed. Store-bought onigiri is wrapped in such a way that the nori doesn’t touch the rice until it is unwrapped so it stays crisp, but we rather like the homeyness of plainly-wrapped rice balls with chewy nori.

Common onigiri fillings include flaked salmon, gingery chicken, spicy fish roe, bonito flakes moistened with soy sauce, and tiny clams cooked in a sweet soy glaze. But the possibilities are endless — how about smoked trout, canned tuna, chopped pickles, marinated tofu or even cheddar cheese? (Don’t knock it till you’ve tried it!)

Thanks to the salt in the rice, onigiri can remain unrefrigerated for up to 6 hours (8 hours if stuffed with umeboshi, a natural preservative) and should be eaten at room temperature or slightly warm.