Combine 2 cups water, sugar, 2 teaspoons salt, and yeast in a large bowl, stirring with a whisk.
Let stand for 5 minutes. Lightly spoon flour into dry measuring cups, and level with a knife.
Add 5 1/2 cups flour, about 1 cup at a time, to the yeast mixture, stirring until a soft dough forms. Turn dough out onto a floured surface. Knead until dough is smooth and elastic (about 8 minutes); add enough of remaining flour, 1 tablespoon at a time, to prevent dough from sticking to hands.
Place dough in a large bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place (85), free from drafts, 1 1/2 hours or until doubled in size. (Gently press 2 fingers into dough. If indentation remains, dough has risen enough.)Divide the dough into 2 equal portions, shaping each portion into a 12-inch-long loaf.
Place the loaves on a baking sheet sprinkled with 1/2 cup cornmeal. Lightly brush the loaves with cold water.
Sprinkle evenly with 1/4 cup of sesame seeds.
Place a shallow pan of boiling water on the bottom rack of cold oven.
Place loaves on middle rack of oven. Set oven temperature to 40
(Do not preheat oven.)
Bake for 35 minutes or until loaves sound hollow when tapped. Cool on a wire rack.
