The key to this recipe is the corn starch which gives the crispiness. Another important thing is to keep the heat on medium high during the initial stage of cooking, or it might convert to chicken curry.
Depending on what chicken piece you are using, cooking time may vary. I have seen that the chicken drumsticks/legs are the ones which takes longer to cook.
Try to use small pieces with bones because this keeps it moist and more flavorful and makes the cooking process way easier.
The amazing flavor of this fry comes from the ground herbs, so please don't skip that stage. Also if you use fresh ginger and garlic it will make a wonderful difference.