Cut the chicken in 3 inch long and 1/2 inch thick pieces.Marinade it with 1 tsp of soy sauce,egg,cornflour,salt to taste,ginger-garlic paste,1/2 tsp black pepper and keep it aside for at-least an hour.
Now cut capsicum and onion in thin long slices.
Heat oil for shallow frying in a pan and fry the chicken pieces till it cooked perfectly and turn golden brown in color.(Fry the chicken on a medium high flame). Keep aside.
On another pan heat 2-3 tbsp of oil and add chopped ginger-garlic saute it till the raw smell gone now saute onion and whole green chilies with it,when onion become little soft add capsicum fry it till it cooked 75%.
Now add salt,sugar,soy sauce,tomato sauce,black pepper,1/2 tsp vinegar,toss it well. Cook for more 10 minutes and serve hot.
You can change the amounts of ingredients as per your taste.