Sourdough Bread

Let starter come to room temperature. Combine yeast, 1/4 cup water and sugar and stir. Set aside for 5 minutes. Add remaining water, salt and starter. Add 4 cups AP flour, beating. Beat 5 minutes, gradually adding bread flour. Beat another 5 minutes, adding flour until dough pulls away from the sides of the bowl. Knead dough for 20 minutes, adding flour as necessary to prevent stickiness. Dust large bowl with flour, put dough in bowl and turn to coat. Cover with plastic wrap and let rise about an hour. Punch down and rest for 10 min. Line sheet pan with parchment (or Silpat) and sprinkle with cornmeal. Divide dough in half and shape into two tight balls, stretching the top surface of the balls until they are smooth. Cover with tea towel and let rise 45 minutes to an hour. Preheat oven to 400. Bring cornstarch and water to a boil (microwave is ok). Stir until thick and clear. Brush tops of loaves with cornstarch mixture and slash tops in tic-tac-toe pattern. Bake 35 minutes or until done.