Cut boiled potatoes into small pieces and keep aside.
Grate tomatoes to make the puree and remove the skin. You can also grind tomatoes to make a puree.
Now add red chilly powder, coriander powder, turmeric powder, salt and half of the kasuri methi (keep rest of the Kasuri methi aside for further use), mix it well with tomato puree. Tomato paste is ready.
Heat oil in a pan; once the oil becomes hot add whole garam masala and sautés it for few seconds.
Now add cumin seeds and sauté till it becomes light brown.
Now add broken red chilly, asafoetida, grated ginger and sauté it for few seconds.
Now add tomato paste and sauté it on a medium flame for 2-3 minutes or till all the spices gets cooked.
Now add cut potatoes, mix it well with the spices and sauté it on a medium flame for 2 minutes.
Add little water, mix it well and make medium thick gravy. Add water as per your desired consistency but medium thick gravy tastes better.
Lastly add garam masala, mango powder, and remaining kasuri methi, mix it well again.
Garnish with freshly chopped coriander leaves and serve hot with Roti, Paratha, Puri or Rice.
Video
Notes
I have not added green chilly but if you want to eat spicily can add it accordingly.