1. To make the poolish: Combine the flour, water and yeast, and set aside to rest, covered, overnight.

  2. To make the dough: Add the 1/2 cup water and flours to the poolish, mix until combined, cover the bowl, and allow the mixture to rest for 20 minutes.

  3. Add the yeast, salt and olive oil, and knead the dough until it's fairly smooth but not necessarily elastic, about 3 minutes by machine, or 5 minutes by hand.

  4. Place the dough in a lightly greased bowl, cover the bowl, and allow the dough to rise, at room temperature, for 1 1/2 hours, gently deflating it and turning it over after 45 minutes.

  5. Knead in the olives and onions; this will be a messy process, but just stick with it (literally!), and it'll get done.

  6. Shape the dough into a 12" x 6" oval, place it on a lightly greased baking sheet, and allow it to rise for about 30 minutes.

  7. Cut three deep diagonal slashes, all the way through the dough, in the center of the loaf, and pull it apart to form a ladder shape.

  8. Allow it to rise for another 30 to 45 minutes.

  9. Preheat the oven to 400°F.

  10. Bake the fougasse for 20 minutes, or until it's starting to brown. Remove from the oven, and cool on a wire rack.

  11. Store, well-wrapped, at room temperature for 3 days, or freeze for up to a month.