This section is from the book "The International Cook Book", by Alexander Filippini. Also available from Amazon: The international cook book; over 3,300 recipes gathered from all over the world, including many never before published in English. With complete menus of the three meals for every day.
For two quarts of ferment: Procure six small, raw, old potatoes the size of ordinary eggs - the uglier, more common-looking and thicker-skinned the better, but they must be sound. Thoroughly wash till completely free from sand, place in small enamelled pan, pour a quart cold water over, let gently cook until soft, which will take considerable time (or nearly fifty minutes), and drop potatoes and water in which they were boiled into a deep, narrow vessel. The water will have reduced by this time to one pint; if reduced more than a pint add shortening to make a pint. Add six ounces sifted flour, carefully and thoroughly mash potatoes, flour and water with a potato masher until a firm pulp, or for about fifteen minutes. Add a quart cold water (in hot weather; lukewarm in cold weather), then carefully dissolve ingredients with the hand until completely free from lumps and see that the ferment is just to a lukewarm point, before adding yeast. Take up a half cup of the ferment and add to it a half-ounce cake firm, fresh compressed yeast, thoroughly dissolve with the hand, add to ferment and thoroughly whisk with pastry whisk until frothy. Remove whisk, cover vessel, place a heavy dry cloth around and set in warm place to rise during night.
First thing in the morning remove cloth and cover from vessel, then whisk ferment for five minutes and strain through strainer into a stone jar, pressing everything through except skins of potatoes. Tightly cover, place in ice box and use as directed when required, taking care to always briskly shake the jar just before using ferment.
N. B. The above ferment is of wide importance for the purpose of strengthening the preparation of the sponge, lightening and giving a delicious, sweet, succulent taste to bread.