Heat the ghee in a large heavy pan, add the chopped onion and fry till onion is transclucent.
Turn the heat to medium low, add the cinammon, cardamom, cloves and fennel seeds, stir for 5 minutes. Add the ginger and garlic and cook for another 5 minutes stirring occasionally to make sure nothing sticks to the bottom of the pan. Then add the turmeric, ground coriander and chilli powder and fry gently for a minute. Add the tomato purée and stir in enough hot water to make a sauce. Bring to the boil and simmer, stirring occasionally for 20 minutes. Season with salt.
Heat a little oil in a large heavy frying pan and stir-fry the chicken pieces until they turn white.
Add the chicken and chopped tomato, sour cream/yogurt to the sauce and simmer gently until the meat is soft and succulent.
Sprinkle with the coriander and serve with plain rice and yogurt.