Cook the cabbage sprouts in salted water until al dente, drain.
Place the chicken skin side down in a cold frying pan and set the hob to the highest heat. Fry until the skin is golden brown and crispy, turn and lightly brown the other side.
Mix the sake, mirin and soy sauce well and pour into the pan. Simmer until the sauce thickens slightly and the chicken is cooked. Leave the meat to rest briefly and then cut into 1 cm thick slices.
Finely chop the garlic, slice the onion into rings and halve the cabbage sprouts. Heat the sesame oil in a frying pan and sauté the garlic, onion and cabbage for a few minutes. Add the oyster sauce, stir and season with pepper.
Spread the rice on plates, arrange the cabbage and chicken on top. Drizzle with the sauce.