San Francisco Sourdough

The pioneers who marched west in America, who followed the trail into the prairie vastness, or eagerly set forth to pan for gold in California or the Yukon, were hardly able to rely on bakers and grocery stores for an ounce or two of yeast. They took their own leavening: a smidgeon of dough kept back from the last baking which could be reactivated for the next. If it was stored deep inside a sack of flour, it was proof against frosts, heatwaves, even Indian attacks!

So it was that t