Boil the potatoes. Peel them and prick the potatoes with a fork. Fry the potatoes in hot oil till they turn slightly brown. Drain and set aside. Heat oil in a shallow pan and fry the onions to light brown. Grind the coconut, poppy seeds, cardamon, ginger and green chillies to a paste. Add the paste to the onions. Fry till the oil seperates. Add chilli powder,cumin powder and dhania powder and stir for 5 mins. Add the yoghurt , salt and the fried potatoes. Add enough water to cover the potatoes and simmer till the gravy is thick for about 10 minutes. Now add the garam masala powder and mix well. Garnish with the chopped coriander leaves. Eat with chapathi/nan.