In a very large bowl, mix starter and water together. In another bowl, combine flours with salt and pepper.Add the flour mixture, 1 cup at a time, to the water mixture, and stir thoroughly with each addition. Use your hands and continue to add flour until well combined.Knead the dough for at least 20 minutes.Plop dough into a low, round 20-inch pan and cover with olive oil; top with sesame seeds, if using.Cut a small cross in the middle of the dough; then cover with a towel and let rise for 2 hours.Bake in the oven for 20 minutes at 450 degrees, then 20 minutes at 390 degrees, and another 20 minutes at 350 degrees. This makes for a perfect loaf inside and out.