An artificial barm

In breadmaking, there is a historic tradition that runs parallel to brewing of using a barm for fermenting dough. The baker took the foaming froth from the top of the brewing beer, rich in yeast and malt, and used this to start a bread dough on its path to becoming a loaf.

Nowadays, the act of brewing is far removed from every day life and getting hold of some barm is near impossible. Modern alternatives have been suggested, such as Dan Lepard's in "The Handmade Loaf" where a good ale is heated to around 70C before whisking in some flour. When cool, some leavening agent such as sourdough starter is added.

I was surprise to learn that preparation of an alternative barm has been around for a long time. On Google books (again) I found a mention of Artifical Barm in "Martin Doyle's Common things of every-day life" (1857) where chapter 5 is given over to all things bread.

Page 25 lists:

Recipe by Professor Donovan for making Artificial Barm

Boil some sound potatoes until they are perfectly soft and just beginning to break into meal; reduce them to a thin paste with boiling water, add of molasses an eighth of the weight of the potatoes, and about the same bulk as the molasses, of good yeast; all to be well mixed and placed before a fire, if in winter. The mixture soon begins to ferment: when the fermentation is at its height, this yeast is fit for use.

Whilst I might try this one day out of curiosity, I think I'll stick to Dan's version in general - if nothing else, there's usually some left over beer.