Heat the oil in a wok or large frying pan and add the spring and red onions. Cook over a high heat for 3-4 minutes until well browned.
Meanwhile, heat the rice according to pack instructions. Add to the pan with the mirin, soy sauce, ginger and green beans, and cook for 2 minutes.
Stir in the pak choi and beef, and cook for 3-4 minutes until piping hot.
Recipe courtesy of Sainsbury's