This popular Shetland beverage is simply the whey of buttermilk left to ferment in an oak cask, and used at the proper stage. To make the whey, pour enough hot water on the buttermilk to make it separate, and drain the whey off the curd. (This may be pressed and eaten with cream.) Pour the whey into the cask, and leave it undisturbed until it reaches the fermenting, sparkling stage.
It is a delicious and most quenching drink, and sparkles in the glass like champagne. After the sparkle goes off, it becomes flat and vinegary, but may be kept at the perfection stage by the regular addition of fresh whey.