I made this up as I was throwing it together and I didn't measure anything, so the measurements are my best guess. I cook by taste and what will fit in my pot. I'm not a fan of sage but it really works, in moderation, in this soup. If you love sage then add it to your heart's desire. Thyme may also be nice if used sparingly. I might have added several shakes of ground marjoram though it's not a very strong herb. To save on a few calories you can skip the heavy cream and use half and half or just thicken with a cornstarch and milk mixture.
In a large 5-6 qt heavy pot cook down turkey necks in water seasoned with various vegetables, salt, peppercorns & garlic. Cook for about 2-3 hours, adding more water as needed until neck meat is tender and will easily pull from the necks. Remove from heat, take the necks out and put on a plate and set aside to cool. You can pull the neck meat and use in this soup or use it for something else.
Strain the broth to get all of the seasonings out.
In the same heavy pot or Dutch Oven heat the turkey broth until hot, then add half of the chopped onions, half of the sliced celery, and all of the bell pepper and parsley. Bring to a boil then reduce heat to keep it on a low boil and cover. Cook until the vegetables are completely tender.
Season with salt & peppers, and garlic, stir well and taste. Get the seasoning right at this point because you will be adding more later. Turn the heat off and use an immersion blender to puree everything until smooth. The soup will have a greenish hue - it will change later.
Remove cover and bring this back to a very low simmer and add remaining onions, celery, add bay leaves, corn, peas, green beans, carrots, and potatoes. Add a little rubbed sage, about a couple of pinches and stir well. Taste and adjust seasoning as needed.
Allow to slowly cook on the stove, uncovered, until the veggies become tender crisp. Add milk, cream, chives or green onions and parsley. Stir well and continue to cook on low heat, stirring occasionally. Taste often and add more sage if desired, salt & coarse black pepper as needed.
Once soup is thickened to your liking (it won't be extremely thick), stir in butter until melted, then add the turkey meat, stir well and heat through. Enjoy!