Place the turkey carcass (if using) or bones, water, carrots, celery, onion, bay leaves, thyme, and peppercorns into a large stockpot.
Bring the mixture to a boil over high heat, then immediately reduce heat to low, cover partially, and simmer for 2 to 3 hours to make homemade turkey broth. Skim off any foam that rises to the surface during the first 30 minutes.
Remove the carcass and strain the broth through a fine-mesh sieve into a clean pot. Discard the solids. You should have about 8 to 10 cups of broth.
If you used a carcass, shred any usable meat from it and add it back to the broth along with the pre-cooked leftover turkey meat.
Bring the broth back to a simmer. Add salt to taste.
Add the egg noodles to the simmering broth and cook according to package directions, usually 6 to 8 minutes, until tender.
Remove the bay leaves before serving.
Ladle the soup into bowls and garnish with fresh parsley. Serve hot with crusty bread.
Notes
If you skip making the stock and only use pre-made broth, you can skip the 3-hour simmer time and proceed directly to adding the vegetables and noodles.
For a richer flavor, roast the carcass briefly before simmering.
This recipe is a great way to use up every bit of your holiday bird.