Remove all of the meat from the turkey and reserve 3 cups for the soup. If you've cooked your stuffing in the turkey, make sure to remove it all.

Break the roast turkey into 3 or 4 pieces that are small enough that they will fit into your largest pot. Fill the pot with cold water so that the water comes 2-inches above the bones. Bring the pot almost to a boil then reduce the heat so that it is barely simmering. You want the water to move around and a few small bubbles to rise, but not to boiling. Cook for 8-10 hours, leaving the lid off. (See notes if you'd like to use your crockpot instead.)

Strain the turkey stock through a colander into a large bowl and discard the bones. Strain the stock once more through a fine-mesh sieve. You can either use the turkey stock immediately or let it cool and refrigerate it for up to 3 days or freeze it for up to 3 months.

Heat the olive oil in a large pot over medium-high heat. Add the onion and cook for 5 minutes. Add the carrot and cook until it begins to brown in a few places, about 5 minutes.

Add the celery, turkey stock, and reserved turkey meat to the pot and bring it to a boil. Simmer for 5 minutes, or until the carrots and celery are soft. Season to taste generously with sea salt.

If you're using the egg noodles, add them cooked to your soup bowl, ladle in the soup, and garnish with a little sprinkle of parsley.