Pressure cook the potatoes until soft. Peel the skin and keep aside. Once cooled slightly, peel and keep aside
Heat oil in a pan. Once hot, add mustard seeds and allow them to splutter.
Add urad dal and channa dal and sauté until lightly golden. Then add jeera and mix briefly.
Add curry leaves, green chilli and sliced garlic. Sauté for a few seconds until aromatic.
Add the sliced onions and cook until soft and translucent.
Add chopped tomatoes and give it a quick stir.
Add salt and turmeric powder. Mix well and cook until the tomatoes soften.
Pour in approximately 3 cups of water and bring the mixture to a rolling boil. This masala tastes best with a slightly flowy hotel-style consistency.
Once the gravy is well combined and cooked, add the potatoes but roughly mashing with hand. Dont make it into smooth paste. Also while cooking, using the back of the ladle, gently mash some of the potatoes into the gravy while leaving a few chunks for texture.
Cover and cook on medium flame, stirring occasionally.
Cook until you reach your desired consistency. Turn off the flame, garnish generously with fresh coriander leaves and serve hot.