Drain the chickpeas and reserve the cooking liquor.
Heat oil in a saucepan and cook mustard seeds and salt until seeds pop.
Add chilli powder, ginger, chickpeas, tomatoes, and curry leaves, cooking until tomatoes soften.
Pour in 200ml of reserved liquor and simmer, adding more if the mixture dries out.
Toast the whole spices in a dry pan and grind with salt to a fine powder.
Scoop out baked potato flesh and divide into two bowls in a two-to-one ratio.
Mix flour into the larger potato portion and spices, chilli, and coriander into the smaller portion.
Shape 110g balls of plain potato and flatten into rounds with floured hands.
Shape 55g balls of the spiced potato mix and wrap the plain potato rounds around them.
Shallow fry the potato cakes in hot oil until they are brown and crisp on all sides.
Drain on paper and serve with the garnished chickpea sauce.