Preheat your oven to medium-high and cut or tear the Dark Rye Bread into chunks. Spread the pieces on a baking sheet and toast until deep brown and slightly charred at the edges—this toasting builds the characteristic malted, caramelized flavor.
Place the toasted bread in a large heatproof container and pour just‑boiled Water over it so the bread is fully submerged. Cover and let steep for at least 3–4 hours, or overnight for a richer extraction.
Strain the liquid through a fine sieve or cheesecloth into a clean pot, pressing on the solids to extract as much liquid as possible. Discard the spent bread solids.
While the liquid is still warm (not hot), stir in Granulated Sugar until dissolved; sweeten to taste—the sugar feeds the yeast and balances the tartness.
Allow the sweetened bread liquid to cool to lukewarm. Meanwhile, dissolve a small pinch of Active Dry Yeast in a little warm water to bloom (about 5–10 minutes), then stir the yeast mixture into the cooled liquid.
Transfer the mixture into a clean fermentation vessel or into individual bottles or jars. Add a few Raisins to each container—raisins help kickstart fermentation and add a gentle fruity note.
Cover the containers loosely (airlock or a cloth secured with a rubber band) and leave at room temperature to ferment for 24–48 hours, tasting periodically. Shorter time gives a sweeter, milder kvas; longer time produces more tang and carbonation. If bottling, use sturdy bottles and check pressure frequently.
When the kvas has reached desired flavor and fizziness, strain out solids and raisins, transfer to clean bottles, and refrigerate to slow fermentation. Chill thoroughly before serving.
Serve cold, pouring gently to leave sediment behind. Enjoy within a week or two for best fresh flavor and controlled carbonation.
