Make the potatoes the day before, press them through the potato press while still hot.
A day later, separate the egg, knead the potatoes well with cornstarch, egg yolk, flour, salt and nutmeg. Shape into a rectangle about two fingers thick on a wet plastic sheet. From this, cut rectangles two fingers wide and just under a finger long. Form these into rolls.
First coat them in egg white, which has been beaten a little with a fork, then in breadcrumbs all around.
In a deep fryer filled to about one third or in a saucepan at 180 °C, fry 3-5 pieces at a time until golden brown. Drain well on kitchen paper.