Into 1/2 cup of milk sprinkle the sugar and the yeast, then mix with a little flour. Sprinkle the top with 1/2 tsp flour, cover and leave at room temp to rise.
Sift rest of flour into deep bowl, make a well and add the leavening agent. Add the still warm mashed potatoes, 1 tbsp oil and the lukewarm salted milk to make a stiff dough then beat with a wooden spoon or mixer until bubbly. Sprinkle the top with another tsp flour and cover. Put in a warm/draft-free place for about an hour to raise to twice its original size.
Tear pieces of dough and pull them into thin, palm sized shapes. Put them into plenty of very hot oil, and fry one side with the lid on the pan, then remove lid and fry other side until crispy.
Says in book: This is a popular snack served with salt and garlic (though also good with sour cream and cheese...or all four!)