Combine 2 cups flour, sugar, undissolved yeast and salt in large mixer bowl. Heat sour cream, water and butter until very warm (120 to 130oF); stir into flour mixture. Stir in 1 egg and enough remaining flour to make soft dough. Knead on lightly floured surface until smooth and elastic, about 4 to 6 minutes. Cover; let rest 10 minutes.
Divide dough into 12 equal pieces; roll each piece into smooth ball. Cover; let rise in warm, draft-free place 20 minutes.
With scissors, make 6 (3/4-inch-deep) snips, from top to bottom, around outside edge of each roll. Beat remaining egg; brush on rolls. Sprinkle with sesame or poppy seed. Bake at 400oF for 10 to 12 minutes or until done. Remove from sheet; let cool on wire rack.