Boil the chicken in milk and salt till the chicken becomes tender. In a separate pan, heat the oil and lightly fry the ginger & garlic paste and green chillies. Add the chicken and milk mixture to the pan. Mix the cornflour in a little cold milk, and add it to the pan, stirring the pan continuously. When the gravy starts thickening, add the pepper powder, stir the pan a little, and serve hot with rumali rotis.