In pot, add water and bring it to boil, add chick peas, turmeric powder, salt, red chili powder, red chili crushed and mix well.
Add sugar,tamarind pulp,tomato ketchup and mix well.
Dissolve corn flour in water and gradually add corn flour+water in a pot and mix well.
Add potato and mix, cover and cook for 2-3 minutes.
Add tomatoes, green chilies, onion and mix well.
Add coriander, chaat masala and mix.
Garnish with onion, coriander, papri and serve.