Heat oil in big pot. Fry onions till golden then take them out leaving the oil in the pot.
Blend onions with yogurt in blender till a paste is formed.
Heat the leftover oil from the onions and add ginger garlic paste, coriander powder, red chilli powder & salt. Saute for 2-3 minutes.
Add the blended onion & yoghurt mixture. Cook on medium heat, and stir the mixture constantly till it turns a golden brown colour from an initial cream-ish colour. If the spice mixture is sticking to the bottom, add water in small increments. This process is called "bhunna" in Urdu / Hindi and is complete when oil can be seen on top of the masala.
Add 3 cups of water to the masala and let it come to a boil.
Once the curry is at a boil, add the chicken koftas / meatballs and cook for 5 minutes. Be careful while adding the koftas so that they don't break, and instead of using a spoon move the pot around using kitchen towel / pot holders to incorporate the kofta's in the salan/curry. The reason being that since the koftas are made from chicken, they are quite soft and prone to breaking, hence the best method is to swirl the pot around with a spoon only being used if required.
Cook on high flame for 10-12 minutes, then let it simmer for around 30 minutes till cooked. Gravy can be adjusted on personal preference - I prefer a thinner gravy, but quite a few people prefer a more thicker gravy.
Garnish with green coriander right before serving.
Serve with a simple salad of sliced onions, salt, vinegar and fresh coriander along with fresh roti and/or steamed rice.