Pare potatoes and cut in slices. Cook until very soft in three cups of water. When cooked rub through a sieve and cool. There must be two cups of this mixture.
When the mixture is about 80 degrees Fahrenheit, pour in the mixing bowl and add yeast, shortening, sugar, and salt. Stir to thoroughly dissolve and then add flour. Work to a dough and then proceed as in the straight dough method.
When the dough is ready for the pans, cut or divide into six pieces and mould into loaves, three inches thick and twelve inches long, and set to rise like the Vienna bread, then bake, using the same method.