Zuzu, I do know what Kvass is and yes, I've learned to make it. Some of it is pretty nasty stuff and some is more than decent.
However, my brewing background is totally catholic (if you set aside my Methodist grandparents from Kansas...)

I've been reading a book: "Sacred and Herbal Healing Beers: The Secrets of Ancient Fermentation" Paperback – September 18, 1998 by Stephen Harrod Buhner (Author) and it's blown me out of the water! MR