Reader Richard, I’d be happy to tell you. Imagine yourself as a peasant living somewhere in Europe anytime before, let’s say, World War II. Bread is a staple of your family’s meager diet, but being a laborer you live in a one-room hut somewhere on or near the land you work. You have no oven, no kitchen to speak of either. You bake your bread off-site somewhere in some sort of communal oven apparatus run by the owners of the estate that employs you.
You’re paid not in money but in cheap, coarse flour which is usually cut heavily with rye or barley. Each week you turn that pay into bread which you and your family eat over the course of many days. You bake one large loaf once a week. Luckily for you coarse rye breads don’t stale very quickly. Still by the end of the week you’re softening any uneaten crusts that are left by cooking them in broth.
But I digress. While you may bake your bread off-site you must make the dough at home. You can’t just mix it up the night before and bake it since you have no yeast, only a scrap of old dough from the previous week’s batch. That bit of “starter” could never grow fast enough to leaven a whole loaf of bread overnight. By the same token you can’t just mix your dough up all at once several days ahead of time, it will over-proof and/or dry out before you can bake it.
The solution to the conundrum: feed your dough slowly over the course of many days or even a week. That way it grows steadily and only fully “ripens” by baking day. It also has a heck of a lot more flavor, though being a peasant, your bread’s flavor isn’t really at the top of your priority list. Still you’ve got a handy system going there, and it’s one we’re going to imitate this week with our pumpernickel recipe.