Peel the potato & chop into chunks. Boil in salted water for 15 minutes until tender,then drain. Pass through a potato ricer or mash. Leave to cool.
Heat the oil in a frying pan & fry the onion until soft.Throw in the chilli & spices, then cook for 2 minutes more until aromatic.Add the mashed potato, coriander leaves & stalks, lemon juice & a sprinkling of salt, then mix well & set aside.
For the batter, sift the flour, turmeric & bicarbonate of soda into a bowl with the salt & water to make a thick batter.
Roll the potato mix into walnut-size balls. Heat the oil in a pan, until a chunk of bread dropped in sizzles & turns golden. Bit the balls in the batter, then fry in batches.