[Ingredients:] 1 pood rye flour; 3 lbs each wheat flour and buckwheat flour; 1 garnets each barley malt, rye malt, and wheat malt; 2 glasses yeast; and ½ lb mint. These proportions will yield at least 12 pails kvass.
Pour the rye flour and the malts into a tub or vat. Set aside 1 lb each of the wheat and buckwheat flour and add the rest of the flour to the vat. Pour in enough warm water to make a thick dough. Bring a kettle of water to a boil, pour the boiling water into the dough all at once, and stir until smooth. When the oven has been heated, prepare 2 kettles, ladle cold water into them, immediately add the dough, and set in a very hot oven that has been swept out, but with hot coals left on both sides. Seal the oven [door] with clay. On the next day—that is, after 24 hours—remove the kettles and top them up with warm water. Set aside for 1½–2 hours, until the crusts are soaked. Return all the dough to the vat, mix thoroughly, and add 2 pails boiling water. Mix again, add 4 pails cold water, stir several times, add a small piece of ice, and let the mixture settle.
Meanwhile, prepare a leaven by pouring the remaining 1 lb each of wheat and buckwheat flour into 2 ladles of the just-settled wort. Add 2 glasses yeast, mix, cover, and set in a warm place to rise. When the must in the tub has completely settled, pour off the 6 pails of liquid into a 12-pail keg and add the raised leavened dough. Pour another 6 pails of cold water onto the dough that remains in the tub, mix several times, let settle again, and pour off into the same large keg.
Take a little of this kvass, add some mint, and bring to a boil. Remove from the stove, cover, and let cool. Strain into the keg or add the mint leaves as well. Plug the keg securely and transfer the kvass to the cold cellar in summer, or, in winter, to a dry basement where it will not freeze. The kvass may be used after 2 days.