Put the potatoes in a large heavy saucepan and cover with cold water, add half of the turmeric and 1 pinch of salt and boil. Cook for ten minutes until the potatoes are tender. Drain the water.
Heat the ghee in a large heavy frying pan. Add the curry leaves and dried chili and sauté, stirring frequently, for a few minutes until the chili begins to blacken. Add remaining turmeric, fresh black cumin, mustard seeds, chilies, cumin seeds and onions, asafetida, fennel seeds and coriander and sauté for 5 min, stirring throughout, until onions are soft.
3. Pour in the potatoes and cook over low heat, stirring frequently, for 10 min. until the potatoes are hot another time. Drizzle with lime juice and bring to table on the spot.
Tip Asafetida is digestive and helps relieve flatulence. The powder is easier to prepare than the tuber. However, it loses its flavor quickly, so keep it in a tightly closing jar.