In a medium pan, add a teaspoon oil and heat on medium low heat for a minute.
Add in the mustard seeds and wait for them to sputter.
Add in the asofetida and curry leaves and mix
Add in the coriander, cumin seeds, turmeric, garlic, ginger and chili and cook for 2 minutes.
Add in the tomatoes, salt and sugar and cook on medium low heat for 10-15 minutes, until the tomatoes are all mixed and mashed up. Adjust salt and sugar for sweet and sour taste.
Add in the chopped boiled potato and water and mix well.
Cook for another 10 minutes.
Serve hot topped with fresh cilantro and some Pooris/Rotis or Rice!