Gently whisk together the cornflour, soy sauce, sherry and chicken stock in a small bowl. Set aside.
Heat the oil in a large wok or frying pan. Add the ginger and garlic and cook for 1 minute. Add the onion and mange tout and stir-fry for a further 2 minutes.
Add the pork and the soy sauce mixture and stir-fry for 2 minutes, until the pork is warmed through and the sauce has thickened.
Meanwhile, cook the rice according to the instructions on the packet. Serve with the stir-fry and garnish with the spring onions.