Soak the magic yeast cake in a little luke warm water. Add a little flour to this, and let it stand an hour. Boil the potatoes in 2 quarts water: when soft put through sieve and then set aside to cool in the potato water. Add to this the lard, salt and sugar.
About 4 in the afternoon put the liquid in large bread riser. Add about 3 quarts of flour, beat thoroughly for at least 10 minutes; now add dissolved yeast to it; let sponge rise until going to bed and then stiffen. Knead until dough does not stick to the hands about 20 to 25 minutes. It will double in size. In morning put in bread pans and let rise one hour or more. Bake in moderately hot oven one hour.
Many persons prefer stiffening the bread in the morning. In this case set the sponge later in the evening and allow it to rise all night, stiffening with the flour in the morning instead of the evening. Of course this allows the baking to be rather late in the day.