Heat 1 tbsp oil in a non-stick pan (medium flame) add mustard seeds, curry leaves, 1 tsp turmeric powder, potato and salt. Stir well.
Make medium size balls from above mixture and keep them aside.
In a bowl, add besan, red chilli powder, remaining turmeric powder and water. Mix well until you get a smooth batter.
Heat remaining oil in a kadhai (medium flame). Dip the potato balls in the gram flour batter and deep fry until golden and crisp on the outside.
For Garlic Chutney- In a non-stick pan (medium flame) add all chutney ingredients and roast for 1-2 minutes. In a mixer jar add roasted spices and grind until you get a coarse powder.
For assembling- Spread 1 tbsp burger mayonnaise on each pav, sprinkle little garlic chutney, place a vada and press gently. Add a dollop of mayo. Serve.