Dissolve yeast in warm water in a large bowl. Add 1 teaspoon sugar; let stand 5 minutes. Add remaining 5 teaspoons sugar, 4 1/2 cups flour, milk, oil, and salt; beat at medium speed of a mixer until smooth. Stir in 2 cups flour to form a soft dough. Turn dough out onto a lightly floured surface. Knead until smooth and elastic (about 10 minutes); add enough of remaining flour, one 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, 45 minutes or until doubled in bulk. Punch dough down, and divide in half. Working with 1 portion at a time (cover remaining dough to keep from drying out), roll each portion into a 14 x 10-inch rectangle on a lightly floured surface. Roll up each rectangle tightly, starting with a long edge, pressing firmly to eliminate air pockets; pinch seam and ends to seal. Place rolls, seam side down, on a large baking sheet coated with cooking spray. Cover and let rise 30 minutes or until doubled in bulk.
Uncover dough; using a sharp knife, make 4 diagonal cuts 1/4 inch deep across tops of loaves. Combine 2 teaspoons water and egg white; brush over loaves. Sprinkle with poppy seeds. Bake at 375° for 30 minutes or until loaves sound hollow when tapped. Remove from pan; let cool on wire racks.