Bring 2 C broth, reserved turkey neck and trimmings to simmer in a dutch oven over high heat. Cook at a high simmer, stirring occasionally, until all liquid evaporates and neck and trimmings begin to sizzle, about 20 minutes. Continue to cook until a dark fond forms on bottom of pot, about 4 minutes longer.
Reduce heat to medium high. Add onion, carrots, celery, parsley and thyme sprigs, garlic, salt and pepper. Cook, stirring frequently, until onion is translucent, about 8 minutes.
Stir in wine and bring to a simmer, scraping up all the browned bits on the bottom of the pot. Add remaining 4 cups broth and bring up to a simmer over high heat. Rescue heat to medium-low, cover, and simmer for 1 hour.
Strain stock through a fine mesh strainer and discard solids. Set aside. You should have 3 1/2 to 4 cups of stock. At this point you can refrigerate the stock for up to 2 days.