Boil, cool, peel and roughly mash the potatoes. Grind green chillies and garlic together in a mixer and make a paste. In a bowl mix mashed potatoes, garlic-green chillies paste, coriander leaves, quarter teaspoon of turmeric powder and salt.
Heat two tablespoons of oil in pan, add mustard seeds, when they crackle, add curry leaves, asafoetida. Remove from heat and add to the potato mixture. Add lemon juice and mix well. Make equal sized balls of the above mixture. Keep aside.
Take besan in a bowl, add soda bi-carbonate, remaining turmeric powder, red chilli powder, salt, one tablespoon of hot oil and enough water and whisk to make a batter of coating consistency. Cover and rest the batter for fifteen minutes.
Heat sufficient oil in a kadai. Dip the potato mixture ball in the batter and deep fry till golden. Drain and place them on an absorbent paper. Serve hot with coconut chutney or spicy garlic chutney.