This is one of those snack foods that Indians munch noisily while watching Indian movie epics in which bandits chase weeping, but upstanding heroines and scantily clad girls shake their hips at the dashing heroes.
Put the onion, garlic and red chilli into a blender or food processor. Blend to a paste, pushing down with a rubber spatula, if necessary. Empty the paste into a bowl. Add the cumin and coriander and mix them in.
Peel the potatoes and cut them into 3mm/⅛ inch thick slices. You may use a mandolin, food processor or knife to do this. Stack about 5 slices together