Mix together the chicken, egg, cornflour, garlic and ginger paste, and enough water so that the chicken pieces are 'coated' with the batter. Leave thus about half an hour.
Heat the oil and deep fry the chicken pieces over high heat to begin with and then lower the heat till chicken is cooked through. Drain on absorbent paper till required.
Heat 2 tbsp oil in a wok, and stir fry the onions in it over high heat till they look 'wet'. Add the green chillies and stir a few times, add the remaindered salt, soya sauce, vinegar, and the chicken.