Mix potato, onion, gram flour, green chillies, ginger, cumin seeds, coriander seeds, fennel seeds, soda, salt, coriander leaves.
Add sufficient water to make thick batter.Heat oil in a kadai. Drop a spoonful of batter in oil and deep fry the pieces till three fourth done.
Drain on an absorbent paper.Break into smaller pieces and refry in the same oil till crisp and cooked. Drain on an absorbent paper. Serve hot with tomato ketchup or mint chutney.