Heat oil in a non-stick pan. Add cumin seeds and sauté lightly. Add carrot, green peas, ginger, green chillies, red chilli powder, turmeric powder, garam masala powder, salt and sauté on medium heat for two minutes. Transfer onto a plate and cool.
Add mashed potatoes, coriander leaves and amchur powder and mix well. Adjust seasoning. Divide this mixture into eight portions and and shape into four-inch long cylinders and shallow fry in sufficient hot oil till light golden.
Drain on absorbent paper and set aside. To prepare the frankie, place a roti on a flat working surface, spread a teaspoon of green chutney all over the roti. Place a potato roll on one side.
Sprinkle some sliced onions, drizzle one fourth teaspoon of vinegar, sprinkle chaat masala over it and roll the roti. Similarly prepare the rest of the frankies, wrap in aluminum foil and serve immediately.