To prepare the chickpea stew, drizzle some oil in a hot pan and sprinkle the cumin seeds along with garlic and ginger. In few seconds, once the cumin seed starts to splatter, add onion and season with salt. Once the onion turns mild golden shade, drop the boiled/canned chickpeas. Stir and add cumin powder, coriander powder and chili powder. Allow it to cook for a few minutes and then add some water to make thick gravy. Mash the chickpeas lightly and add garam masala powder. Check for salt and add any, if required. Once the chickpea stew is done, keep it aside to be used later.
To prepare the aloo tikki (potato fritter), mash the boiled potatoes and put it into a mixing bowl. Add cumin powder, coriander powder, salt and corn flour. Give it a mix and shape several patties out of it. I like to keep it roughly circle and not too thick. To fry the patties, add enough oil in a pan and once the oil is hot enough, drop the patties carefully and allow it to fry until golden brown on both sides.
To prepare the chaat, layer two to three potato patties on a plate. Spoon some chickpea stew on top followed by the sour yogurt, the red and green chutney, chopped onion and fresh cilantro. Finally, add a little bit of sev, squeeze little bit of lime juice and sprinkle chaat masala.
Serve immediately.