Soak samak & sabudana together in water for 4–5 hours.
Grind to a batter with chilies and water till smooth.
Mix in mashed potatoes and sendha namak.
Rest the batter for 10–15 minutes.
Heat the tawa and grease it lightly with ghee or oil.
Spread the batter like a dosa and cook on a medium flame.
Crisp it up with ghee, flip if needed, and serve hot with vrat chutney or curd.