Make a deep slit in one side of the chillies and de-seed.
Put the chillies in a large bowl.
Pour in 500ml / 18fl oz (2¼ cups) water and add a little salt.
Set aside.
Cook the potatoes in a pan of boiling water for about 20 minutes, or until soft.
Then drain and allow to cool.
When the potatoes are cool, peel off their skins, return to the pan and mash.
Season with salt to taste.
Then add the amchoor, chopped coriander, sugar and ground cumin and mix to combine.
Fill the chillies with the mixture.
Pour the flour in a bowl.
Whisk in enough water to make a smooth batter.
Heat enough oil for deep-frying in a kadhai or deep, heavy-based pan to 180 degree C / 350 degree F, or until a cube of bread browns in 30 seconds.
Working in batches, dip the chillies in the batter and then carefully dip into the hot oil.
Deep-fry until light brown and crisp.
Remove with a slotted spoon.
Drain on kitchen paper (paper towel).