In a pan, heat oil and add chopped onions, tomatoes, and ginger-garlic paste. Saute for 2-3 minutes.
Add boiled and mashed potatoes, red chili powder, garam masala, and salt to taste. Mix well and let it cook for 5-7 minutes until the filling is well combined.
Heat a dosa tawa and pour a ladleful of dosa batter. Spread it in a circular motion to make a thin dosa.
Add 2-3 tablespoons of the potato filling on top of the dosa and spread it evenly.
Spread the red chutney on the other side of the dosa.
Fold the dosa into half and garnish with coriander leaves.