Slice the king oyster mushrooms and onion after cleaning them.
Heat cooking oil in a pan and stir-fry the onion and king oyster mushrooms.
Add the beef brisket and stir-fry over high heat.
Season with soy sauce, sugar, minced garlic, and pepper.
Place the sautéed ingredients over rice.
Garnish with chopped scallions and sesame seeds to finish.