Grind green chillies and garlic to a paste. Place potatoes, garlic-green chilli paste, coriander leaves and salt in bowl. Heat two tablespoons of oil in a pan. Add mustard seeds. As they crackle, add curry leaves and asafoetida.
Remove from heat and add to the potato mixture. Add one fourth teaspoon turmeric powder and lemon juice. Mix well. Make eight balls of the above mixture. Set aside. Take besan in a bowl, add soda bicarbonate, remaining turmeric powder, red chilli powder, salt and one tablespoon of hot oil.
Make a batter of coating consistency using water as required. Take tomatoes and slice off tops. Scoop out seeds using a small spoon. Fill potato mixture in each tomato. Heat sufficient oil in a kadai.
Dip the stuffed tomatoes in the batter and deep fry in medium hot oil till golden brown and crisp. Drain on absorbent paper. Serve hot tomato wadas with coconut chutney or spicy garlic chutney.
You can also serve them sandwiched in pao.