Break up the carcass and place in a large pot with Bay Leaves, Salt and Pepper, Rosemary, Marjoram and Thyme.
Allow to simmer for 2-3 hours. Strain. This is your stock.
Melt 2 T. butter in a large saucepan. Gradually stir in the flour until smooth. Slowly stir in the strained stock (which should amount to about 2 quarts) and bring to boil. Add rice and simmer.
Saute the onion and mushrooms in the remaining butter until soft. Add the celery and saute for another 5 minutes. To the simmering turkey stock, add the onions/mushroom mixture along with the parsley, turkey meat, gravy and dressing.
Press the chestnuts through a sieve (or a processor) and add to the soup along with 3T of port.
Adjust the seasoning, adding more salt, in necessary. Simmer for about 2 hours and enjoy!