Slice the onion and green onion thinly.
Cut the beef into bite-sized pieces.
Heat oil in a pan and stir-fry the beef.
When the beef is halfway cooked, add the onion and green onion and stir-fry together.
Add soy sauce, sugar, and cooking wine, and stir-fry until the seasoning is well absorbed.
Place the stir-fried mixture on top of rice.
Optionally, top with an egg yolk or sesame seeds to finish.