Cook the noodles in boiling water for 2 to 4 minutes.
Test frequently so they don't overcook.
Drain well and toss with sesame oil.
Refrigerate, covered, at least 2 hours, overnight if desired.
Combine all remaining ingredients except scallion and mix well.
Since the sesame paste is often very difficult to mix well, you can put it in a food processor with steel knife and some of the liquid.
Add the garlic and ginger, and while the sesame paste is being blended, the garlic and ginger will be finely minced.
If the sauce is not being used immediately, it can be refrigerated, but before serving over noodles, bring to room temperature.
Stir noodles with sauce and serve topped with scallion.
NOTE TO COOK: Carry noodles mixed with sauce to party in serving bowl tightly covered with plastic or in container with tight fitting lid.
Carry chopped scallion separately.
Just before serving, toss noodles and sprinkle with scallion.
All ingredients available at Oriental market.
If fresh Chinese noodles are not available, use American dried spaghettini or linguine and cook according to package directions.
The Oriental sesame paste is preferable to tahini because it has a toasted flavor, but tahini can be substituted.