A week or two ago my friend Kate gave me a gift of cultured culture. It's a North Adams sourdough, cultivated by artist Eryn Foster as part of Oh, Canada, a large scale exhibition of Canadian art at MASS MoCA. Foster "spent two weeks foraging for wild yeast all over North Adams in areas of natural, cultural and geographic significance." Then she generated this bubbly sourdough starter. Now interested museum visitors can ask for samples, and receive them in pint jars. That's what Kate brought to me. (For more on this, try Wild yeast and Care and feeding of Sourdough -- both by Kate, in the Berkshire Eagle and on the Berkshires Week blog.)

I followed the instructions which came with it: fed and watered it, let it sit overnight, marveled at its yeasty bubbly aroma, pungent and sour. Put some back into the fridge for next time. Used some to bake a few loaves of bread -- my first sourdough! They turned out beautiful, with a golden-brown crust, an airy crumb, and -- after an overnight rise in the fridge, followed by an all-morning proof -- a lovely gentle sour. Suddenly I was reminded that once upon a time, all leavened bread must have been sourdough.

Sourdough challah, first rise.

Of course. I should have thought of that sooner. This is, after all, a theme on which I teach each spring as Pesach approaches. The Hebrew word for something which is leavened is chametz, from the root meaning "to sour or ferment." Leavened bread involves fermentation. (Matzah does not. It's made of the same ingredients as leavened bread -- water, flour, maybe a pinch of salt -- but is made quickly enough that no leavening, no fermentation, takes place.) It is the very nature of chametz to be sour. Or it was, presumably, when the word came into use.

I used to bake bread every Friday, though these days I don't often make the time. And I've grown to love the weekly ritual of taking Drew to the A-Frame Bakery in Williamstown after daycare on Fridays, where he joyfully clamors for "a challah an' a cookie!" But I was tempted by the thought of Maggie Glazer's Sourdough Challah. I've never tasted a sourdough challah. Would the bread have any of the tang I associate with sourdough? Or would it simply be a rich challah which happens to be leavened only with the natural activity of yeast and flour and time? (For that matter: would it leaven? Or, in the absence of a packet or two of storebought yeast, would I wind up with flatbread?)

Sourdough challah, second rise.

The process was, unsurprisingly, different from the other challah doughs I've made. First I fed and wakened my starter over the course of a long day. Then I took a mere two tablespoons of starter and mixed them into a sponge and let that grow overnight. Then mixed an eggy dough and kneaded the sourdough sponge into that and let it rise all morning. Then shaped braids to proof, a.k.a. rise again. It's a slow journey, but a pleasant one. The sourdough sponge was unbelievably soft, with a texture unlike anything else I know. The braids slowly swelled, going from looking comically small on their baking sheets to looking like pale raw challot.

I realized at the last minute, oven pre-heated and ready to go, that I had used all three of our remaining eggs to make the dough. I'd meant to buy more, but had gotten distracted by other things at the grocery store, and had completely forgotten. So after a bit of googling (and after asking twitter for suggestions) I wound up glazing one in milk, the other in milk mixed with a bit of honey. It was a hot day for baking, but there is always something profoundly satisfying about the magic of turning flour and water (and sourdough starter!) into bread.

Two sourdough challot, cooling.

They didn't rise quite as much as I had hoped; I might have to let them proof longer next time. Still, the fact that I got two braids of challah out of what started life as a small ball of dough leavened with two spoonfuls of starter seems a little bit miraculous. The texture is light, and the bread has a beautiful crumb. And on the whole, the bread is sweet. There's just the lightest tang of sour at the end of a bite, just before I swallow.

They're not quite as beautiful as the one I usually get from the bakery, but the satisfaction of having made them sweetens them for me. As it happens, I had extra things to celebrate on this particular Shabbat. On the previous evening, the membership of my congregation approved my contract for two more years. A new contract, two loaves of homemade bread, and the company of loved ones on the deck at suppertime: what could be finer?

Thanks, MASS MoCA; thanks, Kate; and thanks to the Source of All Who brings forth bread from the earth.