Add the yeast to the water and mix. Add the flour and mix for 2 to 3 minutes or until combined. Dough will be stiff.

Put in dough-rising bowl or medium size bowl and cover. Leave out at room temperature for 12 to 24 hours. The starter should triple in volume and be wet and sticky. If not using right away cover and refrigerate until ready to use.

Thirty minutes prior to baking place a pizza stone in the oven and preheat to 450°F. Cut out or fold 2 pieces of parchment paper to fit the pizza stone.

In a large bowl soften the yeast in the water. Add the potatoes, Biga, olive oil, salt, rosemary and all but 1 cup of the flour. If using a Kitchen Aid mixer, knead with the dough hook for 4 minutes adding remaining flour as needed, until you get a soft, smooth dough. By hand knead 8 to 10 minutes. Turn dough out onto a board sprinkled with rice flour to bring together, adding flour only as necessary. The dough will be very soft.

Put the dough in a lightly oiled bowl, cover and let rise until doubled in volume, about 1 hour. Once raised, divide the dough in half and shape into two discs about 1 1/2-inches high. Sprinkle parchment paper with cornmeal and place discs on parchment paper. Sprinkle with rice flour, cover with a damp towel and let rise for 45 minutes.

Dimple the loaves with your finger tips and sprinkle with olive oil and salt. Place the loaves (with the parchment) on the pre-heated baking stone and bake for 20 minutes or until nicely browned. Let cool before cutting. Enjoy!