First of all, heat two tablespoons of oil in a pan, add chana dal and urad dal to it, add mustard seeds and let it crackle. Add asafoetida, ginger, green chillies, and onions, and let it cook for a few seconds. Add curry leaves and boiled mashed potatoes, and fry. After adding turmeric, red chilli powder, and salt to taste, mix well and fry this mixture for a few seconds. Add chopped coriander leaves, mix well, and turn off the flame. Now heat the dosa tawa on the stove and grease it with a little oil. Spread the rice and urad dal batter by filling it with a ladle. Let it cook for a few seconds. Pour the prepared potato mixture over it and spread it as a layer. Flip the uttapam and roast it from the other side as well. Enjoy this masala uttapam!