Clean, wash and cut chicken into medium pieces. Marinate with ground black pepper and yoghurt for 3 hours. Wash and cut green chillies into big pieces. Wash and quarter tomatoes. Slice onions. Wash and chop cilantro leaves. Heat oil in a heavy based pan. Add sliced onion and garlic paste. Stir fry on medium heat for 8-10 minutes. Add the coriander powder, turmeric powder and green chillies. Stir fry till oil starts to separate. Add the marinade. Add salt. Stirring continuously, cook over medium heat for 12-15 minutes till the gravy dries up. Add 250 ml water and tomatoes. Cover and cook over low heat for 5 minutes till chicken is cooked. Uncover and cook until water dries up and oil starts to separate. Garnish with cilantro leaves. Serve hot with rice, luchi or roti.