Boil potatoes, peel it and mash it, add oil to the pan saute finely chopped onions add green chillies, curry leaves,garam masala powder, salt and turmeric powder mix well, add the mashed potatoes give it a good mix, add red chilli powder and mix well garnish with coriander leaves and mix. Take out mayonnaise in a bowl add mustard sauce mix well. Keep aside.