Wash and soak the sweet rice overnight. The next day, cook both sweet rice and sushi rice in your rice cooker according to the rice cooker instruction. Allow it to cool down
Combine the soy sauce, sugar, sesame oil, tobanjan, miso paste, and sesame seeds together in a bowl and marinate the thinly sliced beef for about 20 minutes.
Measure each rice bun to 80 g and using cling wrap, make the rice ball then flatten them by pressing with your palm to 1cm thick. Set aside. Make 4 rice buns.
Heat 1 tbs of sesame seed oil in a frying pan over medium heat and cook the yellow onion and marinated beef till the beef is brown
Heat a non-sticking frying pan over medium heat and brown the surface of rice buns by brushing with soy sauce. When the rice surface is browned and hardened a little bit turn the heat off.
Place the bottom rice bun on a plate and top with lettuce leaves. Place the beef on top of the lettuce and top with another layer of lettuce. Place another rice bun on top of it.
