1. Heat 50 ml oil in a wok and stir-fry 100 g sliced onion and 1.5 kg thin strips of beef.
2. Moisten with 300 ml water, 50 ml dark soy sauce, 25 ml mirin and 25 ml ginger juice and cook for 2 minutes.
3. Serve in donburi bowls on a bed of boiled rice.