Like a cross between a blonde beer and mead, kvass is a refreshing fermented drink. It's delicious served cold, with a sprig of fresh mint. This recipe is adapted from Mamushka: Recipes from Ukraine and Eastern Europe (Weldon Owen, 2015) by Olia Hercules.
Heat the oven to 400 F, and line a baking sheet with parchment paper.
Arrange the bread onto the parchment paper, and bake for 20 to 30 minutes or until dark brown.
Initial fermentation.
Drop the toasted rye bread into a jar with a tight-fitting lid, cover with water, and then dd the caraway and coriander seeds. Seal tightly. Allow the kvass to ferment for 3 days in a warm spot in your kitchen way from direct light.
Secondary fermentation.
Strain through a fine-mesh sieve or square of cheesecloth, pressing the liquid from the bread to extract as much as possible. Return the liquid to the jar, discarding the spent bread. Add the mint, honey, and sourdough starter.
Seal the jar and allow it to ferment for 2 days in a warm spot in your kitchen, away from light and direct heat.
Bottling.
Transfer the kvass into flip-top bottles, and let them ferment 1 day more. Then transfer to the fridge where it will keep up to 5 days. Serve cold with a sprig of mint.