1. Puree tomatoes.
2. Boil potatoes, cut 3 potatoes into big pieces and coarsely mash the rest.
3. In a pan heat oil, put saunf, methi seeds, kalonji, red chili powder, haldi and kadhi patta.
4. Stir fry for a while. Add pureed tomatoes, keep stirring until it dries up a bit and then put all the potatoes. Mix well.
5. Add 4 cups of water, bring to boil.
6. Add salt and corriander leaves, let it boil for ten minutes.
7. Serve hot with puris.