Combine yeast and 1/2 cup warm water in a small mixing bowl. Let stand 5 minutes.
Combine remaining warm water, sugar, and salt in a large mixing bowl; stir until sugar dissolves. Add shortening and yeast mixture, mixing well. Gradually add flour, stirring until dough leaves sides of bowl. Let rest 10 minutes.
Work through dough with a large spoon for 1 minute; repeat procedure 4 additional times at 10 minute intervals. (Cover bowl during intervals.)
Turn dough out onto a lightly floured surface; divide into 2 equal portions. Cover and let rest 10 minutes.
Roll each portion into a 12- x 9-inch rectangle. Roll up each rectangle jellyroll fashion, starting at long end. Pinch seams and ends together to seal. Place loaves, seam side down, in 2 heavily greased baguette pans sprinkled with cornmeal. (Baking sheets may be used in place of baguette pans.)
Cut 6 diagonal slashes, 3/4- inch-deep, in top of each loaf. Let rise in a warm place (85°), free from drafts, 1 1/2 hours or until doubled in bulk. Combine egg white and 1 tablespoon water; brush on loaves. Sprinkle with sesame seeds. Bake at 400° for 30 minutes or until loaves sound hollow when tapped. Remove bread from pans or baking sheets immediately. Cool on wire racks.