Also called a "sponge" or "starter," this yeast dough ferments for at least 12 hours, deepening the flavor of the bread products in which it is used. I've fiddled with the measurements for a few months, and I'm happy with this product.
For one batch (approximately 2 cups), you'll need:
+ dry yeast, 1/4 teaspoon
+ lukewarm water, 1/2 cup
+ flour, approximately 1 cup
In a bowl, combine water and yeast. Rest for 5-10 minutes, or until foamy. Gently mix in flour; you should have a soft, fragile "dough." Place dough in an oiled bowl; cover, and allow to rest at room temperature. Overnight, the product will transform into the stretchy, sticky mixture shown above.