Heat the oil in the pan or wok on a medium heat. After a few minutes test to see how hot the oil is by popping in a few mustard and cumin seeds. If they fizzle and pop then the oil is ready.
Add the mustard and cumin seeds and curry leaves in very quick succession. Let them fizzle and pop for a few seconds and then quickly add the potatoes. Be careful as the oil may spit at you – you ca