Combine 1 cup flour, sugar, undissolved yeast and salt in a large mixer bowl. Heat sour cream, water and butter until very warm (120° to 130°F). Gradually add to flour mixture. Beat 2 minutes at medium speed of electric mixer, scraping bowl occasionally. Add egg and remaining 1-1/4 cups flour to make a soft batter. Spoon evenly into 12 greased (2-1/2 inch) muffin cups. Cover; let rise until doubled in size, about 1 hour.
Bake at 400°F for 15 to 18 minutes or until done. Remove from pans; cool on wire rack.