Cook the kimchi:In a pan over medium high heat, add a very small amount of oil. Once then pan is hot, add the finely chopped kimchi and sugar (if using). Saute the kimchi until most of the kimchi juice has evaporated, about 3 to 5 minutes. Stir frequently.

Season the rice:When the kimchi is ready, add it to a mixing bowl along with the hot white rice, soy sauce, sesame seeds, and sesame oil. Mix until everything is evenly and well combined. Roughly divide the rice mixture into 5 equal portions.

Shape the rice balls:With gloves on, shape each portion of kimchi rice into a ball. Then make a hole in the rice ball and stuff about 2 tablespoons of shredded mozzarella. Close the rice ball and firmly compact the ball and shape it into a triangle. Repeat with remaining rice and mozzarella.

Alternatively, you can make the rice balls with onigiri molds. If doing so, scoop ½ of a portion into the mold. Indent the rice slightly in the middle and add the mozzarella. Then top with the remaining portion of the rice and press firmly to shape. Repeat with remaining rice and mozzarella.

Pan fry the rice balls:In a large pan over medium heat, add enough oil to generously coat the bottom of the pan, about 1 to 2 tablespoons. Once the pan is hot, arrange the rice balls in the pan and pan fry each side for 2 to 3 minutes or until crispy. Remove them from the pan and let the rice balls cool for a moment before enjoying.