1. Cook the tomatoes in hot water till the skin starts to peel. Turn off the heat and run under cold water and puree them.
2. Heat vegetable oil in a wok and add mustard seeds, curry leaves, chopped ginger, green chillies and asafoetida on a low heat. Stir briefly until aromatic.
3. Add the besan and roast for 2 – 3 minutes.
4. Add the tomato puree and salt and cook till the puree starts to dry out and you see oil on the sides of the pan.
5. Add turmeric powder, red chili powder, and coriander powder. Stir quickly to avoid burning.
6. Add the boiled potatoes and mix well cooking over a low heat for 5 minutes before adding hot water.
7. Let the gravy thicken slightly and use a ladle to gently mash some of the potatoes to further thicken the curry.
8. Cook for another 10 minutes.
9. Serve hot with chopped coriander

Note: You can use raw potatoes, instead of boiled ones but the cooking time will increase.