Sprinkle yeast into warm water in large bowl and stir until dissolved. Add salt. Combine all-purpose and whole wheat flours and add enough to yeast mixture to make stiff dough. Turn out on floured surface and knead until smooth and elastic, 8 to 10 minutes. Shape into ball. Place in greased bowl and turn to grease top. Cover and let rise until doubled in bulk, about 1 1/2 hours. Punch down and let rise again until doubled, about 30 minutes. Divide dough into 8 pieces and roll each out on lightly floured surface to very thin circle about 9 inches in diameter. Place, one at a time, on baking sheet and sprinkle with sesame seeds. Bake at 400F 5 to 6 minutes, or until bread appears dry, lightly browned and blistered. Run palest side under hot broiler until lightly browned. Cool and store in dry place.