The Vada Pav is Mumbai's most popular street food, followed by Pav-Bhaji. Most Mumbaikars would have a Vada-Pav followed by cutting chai (half a tumbler of tea) or Ganna Juice(sugarcane juice). It's Mumbai's answer to a Burger&Coke. Try it at home it's excellent and worth making even though it's quite time consuming.
1 kg. boiled potatoes, peeled and mashed with a fork.
1 tsp mustard seeds
1 tbsp chopped curry leaves
1 tbsp chopped ginger
1 tbsp chopped garlic
1 tbsp chopped green chillies
1/4 cup chopped cilantro
1/2 tsp turmeric
2 tsp salt.

Red Chutney
1/2 cup roasted peanuts
1/4 cup dry coconut, ground and toasted
2 tbsp chopped garlic
2 tsp red chilli powder(pandey chillis, not kashmiri)
1/2 tsp salt.
Put all these in a blender jar and grind, do  not add water, this chutney is dry and coarse(see photo)
Mint Chutney
1 cup chopped mint leaves
1 tsp sugar
1/2 tsp salt
1/2 tsp lime juice
1 small onion
1 green chili(optional)
Put all these in a blender jar and grind to a smooth paste. Cut open the Pav, apply mint chutney on one side, red on the other put the vada in and enjoy. Bon Appetit.
The Vadas
Boil a kg of potatoes(10mins in a pressure cooker)
Open cooker, cool, chop into pieces and keep aside for the next step.
The Tadka
Take a small vessel-there are special ones for tadka(tempering). Heat 2 tbsp oil,add 1 tsp mustard seeds, wait till they crackle,add 1 tbsp chopped curry leaves, 1 tbsp chopped garlic then 1 tbsp chopped ginger, lower heat, add 1/2 tsp turmeric pdr. 1tbsp chopped green chilies and 1/4 cup coriander leaves, put of flame and pour this mixture over the chopped potatoes. Mix with a fork and lightly mash the mixture, let the mixture be coarse, with tiny pieces of potatoes(not a mash). When cool add salt, 1 tsp,mix with fingers and make balls-about 20. These are the Vadas, to be deep fried in batter.
The Batter
I always made this batter bina naap ke(without exact measure)but since I want the reader to succeed I measured everything this time. 1 3/4 cup Chick Pea flour(besan), 1 cup water, 1/2 tsp salt, 1/4 tsp soda bi-carb, use a good whisk and beat it till the mixture is smooth. The Vada-Pav batter is thinner than for pakodas, the idea is to have a thin coating and not a dense one, a thin batter ensures that.
Heat oil in a small kadhai(I use copper or brass) about 500 ml of peanut oil. When the oil is hot(check by putting a few drops of batter) take the Vadas, dip them in batter and gently put them in the hot oil, a small kadhai would take 2 to 3 at a time, do not put more as this cools the oil. You can lift the coated vadas out of the batter and into the oil with a fork, it works, the excess batter flows through and you can gently lower the vada into the oil. Frying 20 vadas would take about 1/2 an hour. The Vadas will not have the  deep brown color as street side vadas, because they use oil which has changed color with prolonged frying, however if you want your vadas to look darker you can add a 1/2 tsp of red chili powder to the batter, it works. The Vadas are done, we move on now to the chutneys.
Red Chutney
This is quite a fiery chutney and so I balance it with a mint chutney which is full of flavour but not hot. I don't serve a sweet chutney(tamarind,date,jaggery)it kills the taste.