Place the wheat and corn bran together in a large pitcher or jar.
Pour the hot boiled water over the mixture and wait until it's cool to the touch (slightly warmer than the room temperature).
Drop the yeast in, crumbled into small pieces, and then add the rye bread. The water must not be hot as it will kill the yeast's ferments.
Next step is to cover the jar with a blanket to keep it warm and let it ferment for 24-48 hours. Usually after 24 hours the borsch is ready to use but leaving it longer gives it a stronger, richer taste. The bran gets deposited to the bottom of the jar while on top there's a clear liquid with a pale white tint and sour in taste. The sourness also depends on the quality of the bran and yeast on top of the fermentation time.