For the stuffing take urad dal in a bowl. Add green chillies, ginger, red chilli powder, salt, coriander leaves and mix well. Add salt to mashed potatoes and mix.
Divide into eight equal portions. Heat a tawa. Take a portion of mashed potatoes in your palm, spread slightly, place a portion of the dal mixture in the centre and gather the edges and shape into a tikki.
Shallow fry the tikkis on medium heat with a little oil till both sides are evenly golden brown. If the potato covering breaks up, add a little cornflour and mix.
To serve place a tikki on a place. Pour some chilled yogurt, green chutney, sweet tamarind chutney over it.
Sprinkle roasted cumin powder, chaat masala, red chilli powder and coriander leaves. Crush a few papdis and put on the top and serve immediately.