Beat the egg with 2 tbsp. of water in a bowl. Dip the chicken pieces first in egg, then roll in cornflour.
Heat the oil in a non-stick skillet or kerahi till very hot. Put the chicken, a few pieces at a time and fry until golden. Remove.
Pour off all but 2 tbsp. of oil and put in the vegetables and stir fry on high heat for 2 minutes. Add the soyabean sauce and stock. Bring to boil, cover and simmer for a couple of minutes more or until the vegetables are crisp tender.
Combine 1 tbsp. Cornflour and water and stir into the boiling vegetables. Cook, stirring constantly, until the sauce thickens and bubbles for 2 minutes. Add the fried chicken pieces.
Serve with rice and a sauce of green chillies in vinegar.