Potato flour is best prepared in autumn, because the potatoes are mealier when they are just dug out of the ground. Wash the potatoes, grate them, and immediately drop them into water. After grating as much as is convenient, mix them with water so that you have at least twice as much water as grated potatoes. Set aside for several hours or overnight. Squeeze out the potatoes over a coarse sieve, mixing and squeezing with your hands. Strain all the water through this sieve, constantly shaking it, because a sediment, which is the flour, will form on the bottom. Cover the leftover pressed potatoes with fresh, cold water, mix, and again let stand, stirring to wash off the flour, and continue as above.
Next pour off the water that has stood on the potatoes, and cover the potato mash on the bottom with fresh water. Shake thoroughly, strain through a sieve, and so proceed until the flour is completely white. Then, for the last time, pour off the water and take out the flour, which adheres in a thick mass to the bowl or tub. Lay it out in pieces on a thick sheet, and, after covering it with another sheet to protect it from dust, set it to dry in a warm room. When the flour is completely dry, pound it, sieve, and store in a dry place. Use this flour for kissels, biscuit tortes, and puddings. It is added to icings for covering tortes, etc.