Steps
1. Heat oil in a pan and add mustard seeds, cumin seeds, and asafoetida.
2. Add curry leaves, green chili, and onion. Saute until onions are translucent.
3. Add turmeric powder, mashed potato, and salt. Mix well and cook for a few minutes. Set aside.
4. In a bowl, mix rice flour, urad dal flour, salt, and enough water to make a smooth batter.
5. Heat a non-stick pan, pour a ladle of batter, and spread it in a circular motion to make a thin dosa.
6. Drizzle oil around the edges and cook until the dosa is crisp.
7. Place a portion of the masala filling in the center of the dosa, fold it, and serve hot.