Combine 1 cup warm water, sugar, and yeast in a large mixing bown; let stand 5
Combine salt, butter, and 1 cup water in a small saucepan; heat until butter melts. Cool to 105 to 115 degrees.
Stir butter mixture into yeast mixture. Add 2½ cups flour; beat at medium speed of an electric mixer until blended. Add remaining 3½ cups flour to make a soft dough.
Turn dough out onto a lightly floured surface; knead 10 minutes Cover and let rise in warm place (85 degrees free from drafts, 1½ hours or until doubled in bulk.
Punch dough down, and divide into 16 equal portions Shape each portion into a 4 x 1½ inch loaf-shaped roll. Place on greased baking sheets. Cover and let rise in a warm place, free from drafts, 35 minutes or until doubled in bulk.
Score tops of rolls with scissors ,making slashes ¾ inch deep and 2 inches long.
Dissolve cornstarch in ½ cup cold water in a small saucepan ,bring to a boil. Let cool slightly. Brush each roll with cornstarch mixture. Bake at 375 degrees for 35 to 40 minutes or until rolls are golden brown.
Recipe by What's Cooking, Mexico? at http://whatscookingmexico.com/2008/07/11/conquering-yeast/