Heat 2 tbsp of oil in a pan. Fry the mustard seeds and cummin seeds, till they splutter. Add the green chillies, coconut, salt, Raisin and cashew nuts. Fry for 5 minutes. Let the mixture cool. Dry grind the bread slices. Add to the mashed potatoes, salt and bread powder. Mix well to make a soft dough.
Take a small portion of the Potato dough, flatten on your palm and fill with coconut stuffing and shape into a small ball. Repeat with the rest of the dough and stuffing. Roll in the beaten egg and deep fry in hot oil till golden brown. Serve with green chutney or tamarind chutney.