At an early post-quarantine Zoom meeting of the Cook’s Illustrated team, my colleague Andrea Geary mentioned that she was unable to find dried yeast at the grocery store to do some at-home testing of an upcoming dinner roll recipe. I remarked that building a sourdough starter from scratch would be a perfect project right now, with store shelves bare of yeast and lots of time on all our hands.

If you don’t know, a sourdough starter—also called a levain—is a mixture of flour, water, and a collection of wild yeasts and bacteria that together serve to leaven bread. These yeasts and bacteria are naturally present on kernels of wheat and on flour ground from them, but it takes time for them to multiply to the point where they can actually produce a loaf of bread.

The process of creating a sourdough from scratch typically involves mixing flour and water together and then letting the mixture sit for a day or more until the dormant microorganisms on the flour wake up. After that, you “refresh” the nascent culture on a daily basis by moving a portion of it to a new mixture of flour and water and discarding the remainder. Sometime after 2 to 3 weeks or so of doing this, the starter will be ready for prime time. Using a typical recipe—my own Cook’s Illustrated one among them—this might churn though a few pounds of flour, all before baking a single loaf of bread.

But given that even flour is a challenge to find these days, people are unlikely to want to waste it, even if it meant a successful starter at the end of the day. That’s why I wondered: What if instead you could create one using just tiny amounts of flour and conserve the bulk of it for the bread itself?