Grease a muffin pan with sesame oil and fill with cooked rice.
Press down with a spoon creating a pocket in the center.
Bake for 15-20 minutes at 200 degrees C.
In a frying pan, combine katsu snack pieces, sliced onions, mentsuyu, cane sugar and water and cook over low to medium heat until onions are soft.
Pour whisked egg on top and cook for another 1-2 minutes.
Transfer cooked mixture into the rice cups and garnish with mitsuba, nori and pickled ginger.