Combine chicken mince, red chilli powder, cumin powder, garam masala powder and salt. Mix thoroughly. Using a tablespoon, divide into equal portions. Roll each portion into a ball. Bring chicken stock to a boil, crush green cardamoms and add to chicken stock.
Add chicken balls to boiling stock, lower the heat and continue to cook until chicken balls are cooked and stock has almost evaporated. Keep aside. Remove stems, wash and chop green chillies. Boil walnuts and then grind to a fine paste. Peel, wash and cut onions into halves. Boil in one cup of water till soft, drain and grind to a paste.
Heat oil, add boiled onion paste and cook till oil begins to separate. Add ginger, garlic paste, green chillies and cook for a moment. Add tomato paste and bring to a boil. Lower the heat. Add fresh cream, stirring continuously. Add koftas and bring to a boil. Adjust salt.