Mix the egg, flour tablespoons cornflour, salt and one tablespoon soy sauce in a bowl. Add the chicken pieces and mix. Set aside for half an hour. Mix the remaining cornflour in one cup of water.
Heat sufficient oil in a wok and deep fry the marinated chicken for two to three minutes. Drain on absorbent paper. Heat four tablespoons oil in a wok, add the ginger and garlic and stir fry for half a minute. Add the onion and green chillies and continue to stir fry for a minute. Stir in the remaining soy sauce, MSG, chicken stock and salt. Bring the mixture to a boil. Stir in the cornflour mixture and cook for a minute more or until the sauce starts to thicken, stirring continuously. Add fried chicken pieces and capsicum and cook for a couple of minutes.
Stir in vinegar and serve hot, garnished with spring onion greens.