Provençal Slit Bread (Fougasse)

Method

1. Prepare the poolish: In a medium bowl, mix the bread flour, yeast, and water until combined. Cover the bowl and let it rest at room temperature for 12 to 16 hours (overnight). The poolish should become bubbly and at least double in volume.
2. Make the dough: In the bowl of a stand mixer with the dough hook, combine the poolish, bread flour, whole wheat flour, water, yeast, olive oil, and salt. Mix on low speed until no dry flour remains. Then knead on medium speed (speed 2 on a KitchenAid) for 5 minutes, until the dough is elastic and fairly smooth.
3. First rise: Shape the dough into a tight ball. Lightly oil a clean bowl, place the dough seam-side down, cover, and let it rise in a warm spot for 1 hour.
4. Fold the dough: Wet your hands or rub them with olive oil to prevent sticking. Grab a section of dough from the top of the bowl, stretch it up, and fold it over the center. Rotate the bowl 90° and repeat until you have completed 4 folds around the bowl. Turn the dough seam-side down, cover, and let it rise for another hour in a warm spot.
5. Shape the dough: Place a 14x16-inch piece of parchment paper on your work surface and lightly grease it with olive oil. Turn the dough out onto the parchment and shape it into a triangle about 12 inches long and 6 inches wide at the base. Let it rest for 30 minutes.
6. Slit the dough: Using a pizza cutter or a sharp knife, cut a slit down the center, stopping about 1 inch from each end. Then make a few diagonal slits on each side of the center slit. Gently stretch each slit open until they are about 2 inches wide, so they stay open during rising and baking. Let the dough rise for 30 minutes.
7. Preheat the oven: While the dough is rising, place a baking stone on the middle rack and preheat the oven to 425°F.
8. Bake: Using the parchment paper, carefully transfer the fougasse to a peel or the back of a sheet pan. Then slide it, parchment and all, onto the hot baking stone. Bake for 25 to 30 minutes, until golden brown.