Heat 2 tablespoons of oil in a skillet over medium heat. Fry potatoes until they turn medium brown, 6-7 minutes, turning often. Remove with slotted spoon and set aside.
Add 1 tablespoon oil to the skillet and heat over medium low heat. Fry red chillies until they darken. Sprinkle asafoetida onto the chillies. Add ginger, green chilli, cumin, red pepper, salt and sugar and stir a few times. Stir in the potatoes. Add water and simmer, covered until potatoes are tender but still hold their shape, 15-20 minutes. Add tamarind and stir gently to mix in with the potatoes.
Remove from heat and let stand covered for 10 minutes to develop the flavours. Garnish with coriander to serve.