Heat the mustard oil till it starts smoking. Reduce heat, add dry red chillies and coriander seeds. When they start spluttering, add asafoetida, stir and add the tomatoes. Cook for 1 minute; add turmeric powder, red chilli powder, and salt. Cook until the tomatoes become soft, pulpy and well blended.

Add 1 1/2 cups water, bring to the boil and add the drained potatoes and green chillies. Cook until they become tender and there is a lot of curry.

Serve garnished with green coriander.