In a large bowl, combine 1/2 cup lukewarm water (105°F–115°F), yeast and sugar, and let stand until foamy, about 10 minutes. Stir in 1 1/3 cups water and salt. Using a wooden spoon, beat in enough flour 1 cup at a time to make a soft dough.
Butter a large bowl. Turn dough out onto a lightly floured surface and knead 8 to 10 minutes or until smooth and elastic, adding only as much of remaining flour as needed. Transfer to bowl and turn to coat. Cover with a kitchen towel and let rise in a warm place 45 minutes to 1 1/4 hours or until doubled in bulk.
Lightly grease 3 baking sheets and sprinkle with cornmeal. Punch down dough and divide into thirds. Cover and let stand 10 minutes, then roll each piece into a 18 x 8-inch rectangle. Starting at a long side, roll up jelly-roll style and taper ends. Place on baking sheets seam side down, then cover and let rise 30 to 45 minutes or until doubled in bulk.
Preheat oven to 450û and place a pan of boiling water on bottom rack. In a small bowl, combine egg white and 1 tablespoon water. Brush on loaves and, using a sharp knife, make a slash in top of each.
Place 1 or 2 loaves on middle oven rack (refrigerate remaining loaf or loaves until ready to bake). Bake 16 to 18 minutes or until bread is golden and sounds hollow when tapped on bottom. (If loaves seem to be browning too quickly, lay pieces of foil loosely over them.) Transfer crusty French loaves to wire racks to cool.