chop the onion and green chili
In a pan heat the oil and temper the cumin seed and saute the onion and green chili for 2 mins
add coriander leaves, turmeric powder and salt and mix well
add boiled potato, mash it and mix well
in another bowl add besan flour, red chili powder, salt and butter milk mix well and make as a batter
take a small ball press it and dip in the batter
heat the oil and deep fry it
In the bread / bun apply any chutney
keep the two vada and close it
now batata vad pav is ready to serve