This section is from the book "Mrs. Lincoln's Boston Cook Book", by Mary J. Lincoln. Also available from Amazon: Mrs. Lincoln's Boston Cook Book.
¼ cup flour.
¼ cup sugar.
1 tablespoonful salt.
3 raw potatoes.
1 to 2 quarts boiling water.
1 cup yeast.
First, see that you have at least three quarts of water boiling rapidly. Pare the potatoes, and keep them covered with cold water. Mix the flour, sugar, and salt in a large bowl, and grate the potatoes as quickly as possible, not stopping to grate every scrap; mix them at once with the flour, using a wooden or silver spoon, that the mixture may not be dark-colored. Pour the boiling water directly from the teakettle over the grater, and rinse off the potato into the bowl, using perhaps a pint of water at first. Mix the water thoroughly with the potato and flour; then add, slowly, enough more boiling water to make it the consistency of thin starch. The amount of water will depend upon the quality of the flour and potatoes. If it does not thicken, pour the mixture into a double boiler or granite pan, and let it come to the boiling-point, stirring well to keep it from sticking. Strain through a squash strainer and let it cool. When lukewarm (clear through the mixture, not merely on the top), add the yeast. Cover slightly, and keep in a warm (not hot) place, until light and covered with white foam. After it begins to rise, beat it well several times, as this makes it stronger. At night, or when well risen, put it into wide-mouthed earthen or glass jars. The next morning cover tightly, and keep it in a cool place. Reserve one cupful or more in a small glass jar, and do not open it until ready for the next yeast-making. Always shake yeast well before using; take your cup to the jar instead of taking the jar to the hot kitchen; when empty, scald the jar and the cover thoroughly. This is the quickest and easiest way of making yeast, fifteen minutes being ample time for the first part of the process. It is whiter and looks more inviting than that made with hops. It keeps well two weeks, and makes delicious bread.
This receipt can be varied by using boiling hop-water.
Steep one fourth cup of loose hops five minutes in three pints of water, in a granite or porcelain kettle, and strain it into the potato and flour. Or the flour may be omitted, using more potato or less water. Many think it an improvement to mix one even teaspoonful of sifted ginger with the flour, sugar, and salt. The hops and ginger will make the yeast dark-colored, but it will not be perceptible in the bread.
Three large, old potatoes, pared, soaked, and boiled until broken in small pieces; half a cup of loose hops boiled in one quart of water. Drain and mash the potatoes; add the hop water and enough more hot water to make two quarts. Strain, rubbing all the potato through, and put it on to boil. When boiling, add three fourths of a cup of flour, which has been wet to a smooth paste in cold water, and three quarters of a cup of sugar. Boil five minutes, stirring well; let it cool; add three fourths of a cup of yeast; and, when well risen, add one fourth of a cup of salt. Keep in a covered stone jar in a cool cellar. Bread made with this yeast will not sour even in the hottest weather.
Steep half a cup of loose hops in one quart of boiling water, in a granite kettle, five minutes. Mix one cup of flour, one fourth of a cup of sugar, and one tablespoonful of salt. Strain the hop liquor, and pour it boiling into the flour mixture. Boil one minute, or till thick. When cooled, add one cup of yeast.
 
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