1Heat 1 tablespoon of vegetable oil in a pan over medium heat.
Add mustard seeds and cumin seeds to the hot oil and let them splutter.
Add the sliced onion and sauté until they turn golden brown.
Add turmeric powder and salt, then mix well.
Add the boiled and mashed potatoes to the pan and mix thoroughly with the spices.
Cook the mixture for a few minutes, then add chopped cilantro and mix well. Set aside.
Heat a non-stick pan or griddle over medium heat and lightly grease it with a little oil.
Pour a ladleful of dosa batter onto the center of the pan and spread it evenly in a circular motion to form a thin dosa.
Drizzle a few drops of oil around the edges of the dosa and cook until the bottom turns golden brown.
Place a portion of the potato filling on one side of the dosa and fold the other side over it.
Serve hot with chutney and sambar.