Boil, peel, and mash potatoes in a bowl.
Heat 1 tbsp oil, crackle mustard seeds and curry leaves, then sauté ginger paste and chopped green chilies.
Add turmeric powder, salt, and tempered spices to mashed potatoes; mix well and shape into balls.
Whisk gram flour, salt, and water into a smooth, pourable batter.
Dip potato balls into batter and deep-fry in hot oil until golden crisp.