Wash and soak the chicken in buttermilk overnight and refrigerate or if you are soaking in the day then it would be at least 4 hours. Drain off the buttermilk fully before marinating. Why do you have to soak the chicken? Just to tenderize the chicken.
Make a paste with the coriander leaves and green chilli, set aside till you use it for seasoning.
Mix all the ingredients for marination and rub the marinade all over the chicken pieces. Set aside for 45 minutes to 1 hour
Cook chicken in a pan or wok on a medium flame till tender and soft. If needed, you can sprinkle a little water (I let it cook in its own juices). If the chicken oozes out the excess then, evaporate by cooking on high.
Time for tempering once the chicken is cooked. Heat a pan with oil, add cumin, and curry leaves and green chillies. Let the leaves turn crisp