Rinse 2 cups of short-grain rice under cold water until clear. Add rice and 2 cups of water to the rice cooker and cook. Let sit for 10 minutes after cooking.

In a bowl, mix miso, mirin, sake, sugar, and butter until smooth to prepare the miso mixture.

Use cling wrap to shape the cooked rice into balls or triangles, packing them firmly.

Heat a skillet, melt 1 tablespoon of butter, grill rice balls 1 minute per side, brushing tops with miso mixture.

For soy sauce, heat vegetable oil, grill rice balls for 1 minute per side, brushing with soy sauce until crispy.

Remove from skillet, garnish with chives and sesame seeds, and serve warm.