It worked better than I thought.
I hesitate to call it a sourdough bread, since it used commercial yeast to rise. But it tasted like sourdough. On a day when I didn't have time for anything more leisurely or complicated, it was pretty darned good.
Sourdough-Flavored Fast-Rise Bread
3/4 cup warm water
2 1/4 teaspoons (1 package) rapid rise yeast
8 ounces (by weight) sourdough starter (at 100 percent hydration)
3 cups (13 1/2 ounces) bread flour
1 teaspoon salt
1 tablespoon olive oil
In the bowl of your stand mixer, combine the yeast and water, then add the starter and flour. Knead until the dough is silky and elastic. Add the salt and olive oil, and continue kneading until both are fully incorporated.
Form the dough into a ball, drizzle with a bit of oil, and return it to the bowl. Cover the bowl with plastic wrap and set aside for an hour, or until the dough has doubled, if it rises faster.
Preheat the oven to 350 degrees and sprinkle some cornmeal on a baking sheet.
Remove the dough from the bowl, and for it into your preferred shape. Cover with plastic wrap and let it rise until doubled, about 30 minutes.
Remove the plastic wrap, slash the dough as desired, and bake at 350 degrees until nicely browned, about 40 minutes.
Cool completely on a rack before cutting.
And here's another yeast/sourdough hybrid.
This has been submitted to Yeastspotting.