Thaw shrimp overnight in refrigerator, keeping it in the bag so you can catch the “juice” when you open it. (In a pinch you can also thaw it inside the bag in a bowl of barely warm water.)
Drain shrimp well, reserving the liquid that accumulates in bag. (I dry shrimp with a paper towel if they’re quite wet.)
Put liquid drained from shrimp in small saucepan and simmer until reduced by at least half. (This will concentrate the shrimp flavor and evaporate the water. Watch carefully, this doesn't take long!)
Cook macaroni in large pot of salted, boiling water according to package directions, or until soft but still slightly chewy. Be careful not to overcook.
Drain macaroni and cool, but don’t rinse.
While macaroni cooks, dice shrimp (discarding the tails), celery, and green onions and put in bowl with a snap-on lid.
Mix dressing ingredients together.
When macaroni is cool, mix it into shrimp mixture in bowl, then gently fold in dressing. (You may not need all the dressing if you prefer your salads to be more dry.)
Season to taste with salt and pepper.
This is best if chilled a few hours before serving. Will keep in the refrigerator for a few days.
