Peel and run potato through the food mill, press through a sieve or smash with a fork.
Work the salt and sugar into the potatoes.
Add half the tapioca flour, plain flour, all the baking powder and the half egg.
Mix until flours get worked in.
Add the remaining flours and continue to work in.
If the dough is too dry, add a bit of milk.
Let the dough sit for 30 minutes.
Roll the dough into 2 cm balls.
Heat the oil until hot and drop the balls into the oil.
Press the balls into the oil so they puff up.
Fry the balls until golden brown and drain.
While frying, pressing the balls down into the oil will encourage the balls to puff, creating a hollow middle.