-all optional Stir the yeast into the warm water & let proof for 10 minutes. Add the remaining water & the biga, then the flours & the salt. Mix with a wooden spoon for 5 minutes. The dough will not pull away from the side of the bowl. Wet your hands & knead on a lightly floured board to ensure that all the ingredients are well mixed. Turn into a lightly oiled bowl, cover with plastic wrap & let rise at room temperature until it has almost tripled in volume, 3 to 5 hours. This dough works very well if left to rise overnight or in the refrigerator. Let it come back to room temperature before shaping. Flour your work surface very well & flour a scaper. Turn the dough onto the work surface, but do not punch down. Divide into 3 equal pieces. Work in your filling if using by flattening the dough & sprinkling equal amounts of filing over the dough. Turn in the sides of the dough & roll each piece into a ball, being gentle but at the same time pulling the skin taut. Place the loaves on floured parchment paper set on baking sheets, cover with a heavy cloth & let rise until doubled, about 1 hour. Preheat the oven to 230ºC . Bake the loaves for 15 minutes. At this point the dough should be set you can remove the paper. Slide the loaves directly onto the baking sheets & bake until crusty & golden, about 30 to 35 minutes.