Soak the mushrooms in warm water for a while and slice them .
Add corn flour and salt to the chicken pieces. Set aside for 10 minutes.
In the meantime add oil in a frying pan and fry the chicken till they turn golden brown.
In a separate pan add 2-3 tbsps of oil .Tip in the crushed ground green chilies, chopped spring onions, chopped garlic, mushrooms and crushed ginger. Cook for 3- 5 minutes.
Then add black pepper, salt and chicken cube mixed in flour and stir fry.
Finally add the chicken, chicken stock, flour, and vinegar and Soya sauce.
Cook for 2 minutes.
Pour the mixture in an oven proof dish and bake for 10 minutes.
Serve with buns.