Mix together sauce ingredients. This may be stored in refrigerator for several weeks. Cook pasta according to package directions. Drain, rinse to cool. Toss with 1 tablespoon sesame or peanut oil to keep moist. Refrigerate for at least 1 hour. Sauce may be added to whole bowl or spooned onto individual servings. Mix together and top with sliced scallions. Serve with chopsticks if desired.