Cook the rice according to pack instructions. Meanwhile, heat the oil in a wok over a high heat until smoking. Add the onion and stir-fry until softened. Tip in the pork mince and stir-fry for 10 minutes until cooked. Stir in the lemongrass paste and ginger and toss for 1 minute until heated through.
Meanwhile, bring a large pan of water to the boil, add the pak choi and blanch until just tender (about 2 minutes).
To serve, stir the chopped spring onions through the rice and divide between four plates, along with the pork stir-fry and steamed pak choi.