Dissolve yeast in 1 cup warm water in a large bowl; let stand 5 minutes.
Lightly spoon flour into dry measuring cups, and level with a knife. Add 2 3/4 cups flour, oil, and salt to yeast mixture, and stir until a soft dough forms. Turn dough out onto a floured surface. Knead until smooth and elastic (about 8 minutes); add enough of remaining flour, 1 tablespoon at a time, to prevent the dough from sticking to hands (dough will feel tacky).
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, 45 minutes or until doubled in size. (Gently press 2 fingers into dough. If indentation remains, dough has risen enough.)
Punch dough down. Cover and let rest 5 minutes. Shape dough into a 21-inch rope; place on a baking sheet sprinkled with cornmeal. (If your pan is not long enough, form the rope into a slight semicircle until it fits.)
Using a pair of sharp scissors held almost horizontally, make diagonal cuts about three-fourths of the way through the dough, leaving about 1 1/2 inches between the cuts. The cuts will form triangular pieces; gently pull all these pieces away from the center on alternating sides.
Combine 1 teaspoon water and egg white, stirring with a whisk. Combine the poppy, sesame, and mustard seeds. Brush dough evenly with egg white mixture, and sprinkle evenly with seeds. Cover and let rise 30 minutes or until doubled in size.
Preheat oven to 400°.
Uncover dough, and bake at 400°for 20 minutes or until the bread is browned on bottom and sounds hollow when tapped. Remove from pan, and cool on a wire rack.