Well, it’s not really a bait and switch, but truth be told, I don’t use old dough and poolish preferments in my baguettes. I use old dough and sourdough starter. However I wanted to put up old dough and poolish instructions because I didn’t want to punish any aspiring baguette makers by forcing them to make a starter first (even though directions are right up here on the site). It would turn a process that’s designed to take 2-3 days into one that could take up to ten. And that’s a lot, even for people who really, really like baguettes. It works out pretty much the same, anyway.
Why do I use sourdough starter in my baguettes instead of a poolish preferment? The answer is of course flavor. Sourdough starter (properly called levain, since “sourdough” is the province of San Francisco). Has a greater variety of yeasts and lactic acid bacteria than a poolish made from store-bought yeast. It’s also, at least I theorize, a bit more “authentic” (though I hate that term) in that it more closely mirrors the “brewer’s yeast” that industrial-era bakers used. Brewer’s yeast is the scum that’s left over from beer-making. As such, it’s rich in a wide variety of microbes including bacteria. Packaged yeast is almost entirely yeast (though contrary to popular belief, there are small populations of miscellaneous bacteria in it). So, I get a broader spectrum of flavor. The consistency is also the same, about 50-50 water to four by weight (or 100% hydration, as bread bakers say). Lastly, it allows me to economize, since starter is something I always have on-hand, and let’s face it, why spend time and energy making a custom component when I don’t absolutely have to? Suffice to say, it works for me.