Cut the pork and onion into bite-sized pieces.
Heat cooking oil in a pan, then stir-fry the pork.
When the pork is halfway cooked, add the onions and sauté together.
Add soy sauce, sugar, mirin, and cooking wine, then simmer.
Once the sauce has thickened, turn off the heat and serve over rice.
Finish by sprinkling green onions and sesame seeds to taste.