Pound the potato, radish, ginger, garlic & green chilies in a mortar and pestle.
Heat 1 tbsp. oil and fry the ginger, garlic and chilies till light brown.
Add the potato & radish and saute for 3-4 minutes on a medium flame till they turn light brown and are half cooked. Keep aside.
Heat remaining oil in a pan and temper with red chilli, cumin seeds and asafoetida.
Now add the onion and fry till light brown.
Add the powdered spices and mix well.
Then add the tomatoes & sprinkle some water. Cover & cook till it is mashed.
Return the fried radish, potato and salt. Give it a stir and saute for 2 mins.
Add 1/2 cup water and cover. Simmer on a medium flame for 4-5 minutes. Garnish with coriander leaves and serve with rice or chapati.
