Heat a pan with little oil, add mustard seeds, whole coriander seeds, asafoetida, & minced green chillies - ginger.
Saute it for a while, and add the curry leaves, followed by minced garlic. Saute for few seconds and then add the turmeric powder.
To this add the boiled & mashed potatoes into it and cook until the mixture is done. After that add salt and coriander leaves and mix well.
In the last add lemon juice.
Keep aside to cool. Once cooled, make golf sized round potato balls.
For the vada batter, mix all the ingredients together, except baking soda. Mix required amount of water to form a semi thick, but flowing consistency batter.
When you are ready to fry the Vada, add baking soda to the batter. Mix well to incorporate air.
Heat ample amount of oil in a kadhai. Once it's hot lower the flame. Add 1 tsp of hot oil into the besan batter and mix it well.
Dip potato balls in the batter and drop them into the hot oil. Deep fry them on medium to low flame. Fry till light golden colour is achieved. Strain them and keep aside.
To make Green chillies - Slit them, remove seeds and fill a pinch of salt. Deep fry in oil after frying the vadas.
How to serve :
Slit the pav, put a little butter and toast them on the tava to just crisp them up a little.
Apply tamarind chutney, Green chutney and Dry garlic chutney on pav.
Place the fried vada inside along with green chilly, squish them together and gobble up.