Wash an trim the chicken pieces, set aside. Heat the oil in a large Kahari. Throw in the onions and fry until they are golden brown. Add the tomatoes and stir well. Add the cinammon stick, cardamoins, peppercorns, cumin seeds, ginger, garlic, garam masala, chilli powder and salt. Lower the heat and stir-fry for 3-5 min. Add the chicken pieces, 2 at a time, and stir fry for at least seven minutes or until the spice mixture has completely penetrated the chicken pieces. Add the yougurt and mix well. Lower the heat and cover the pan with a piece of foil, making sure that the foil does not touch the food. Cook very gently for about 15 min, checking once to make sure the food is not catching on the bottom of the pan. Finally, add the lemon juice, cilantro and green chillies and seve at once.