Warm the multigrain rice for 2 minutes.
While the rice is heating, rinse the perilla leaves under running water and slice them.
Break 3-4 walnuts into pieces and set aside.
Add all ingredients (except cheese) to the multigrain rice, then add perilla oil and black pepper.
Shape the rice balls, place cheese on top, and microwave for 30 seconds to 1 minute.
Enjoy your meal!