Place turkey carcass in a large 6-quart pot. Cover with water, at least ¾ full.
Peel onions, cut into large pieces, and add to pot. Wash celery stalks, slice, and add to pot as well.
Simmer, covered, for about 2 ½ hours.
Remove carcass from pot. Cool soup in the refrigerator (hint: divide soup into smaller, shallower containers for quicker cooling).
While soup is cooling, remove remaining meat from turkey carcass. Discard bones and cut meat into bite-sized pieces.
After soup has cooled, skim off fat from top. Return soup to pot.
Add turkey meat to skimmed soup, along with herbs and spices.
Bring to a boil and add pastina. Continue cooking on low boil for about 20 minutes, until pastina is done. Serve at once or refrigerate for later reheating.