It does mention sherry, but don't think it mentioned the process they use for that is called solera - https://en.wikipedia.org/wiki/Solera https://en.wikipedia.

It does mention sherry, but don't think it mentioned the process they use for that is called solera - https://en.wikipedia.org/wiki/Solera https://en.wikipedia.org/wiki/Solera It's also done with sour beer, but with a single vessel, http://www.milkthefunk.com/wiki/Solera http://www.milkthefunk.com/wiki/Solera has an interesting explanation 'to continuously make sour beer'