In a pan, add oil, mustard seeds, urad dal, chana dal, curry leaves, 2 chopped green chili, 1 tsp ginger paste, 1 medium size onion slice, turmeric powder, salt, and boiled and mashed potatoes. Mix well.
Switch off the gas; add some coriander leaves. Mix well. Potato stuffing is ready.
In a dosa batter, add some water and make it slightly thin.
Add 1 tsp Eno and water. Mix well.
Now heat, tawa and grease it with oil. Spread dosa batter with a ladle.
Sprinkle some coriander leaves on the dosa.
when dosa becomes crisp, spread potato bhaji on the center of the dosa.
Fold the dosa and with chutney and sambhar.