Punch dough down. Turn out onto a lightly floured surface. Cover; let rest 10 minutes. Roll into a 20x9-inch rectangle. Spread sugar mixture atop. Fold rectangle lengthwise into thirds, forming a 20x3-inch rectangle. Slice crosswise into 96 very thin threads, each 1/8 to 1/4 inch wide. For each bun, gently stretch a group of 8 threads until they're about 7 inches long. Wrap threads in a spiral around your first 2 fingers, stretching dough slightly. Tuck the end into the top to seal. Place on a lightly greased baking sheet. Repeat with remaining dough. If desired, sprinkle with sesame seed. Cover; let rise in a warm place for 20 minutes. Meanwhile, in a wok place a greased steamer rack over water. Bring water to boiling over high heat. Place buns on the rack so the sides do not touch. (Cover and chill extra buns.) Cover and steam for 10 to 15 minutes or until buns spring back when touched. Repeat with the remaining buns. Serve warm. Makes 12 side-dish servings.