Preheat the oven to 325 degrees F.
In a small bowl, combine the flour, garlic powder, salt and pepper. Set the venison neck on a plate and coat lightly with the seasoned flour.
Heat a 6 to 7 Quart Cast Iron Dutch oven pot over medium heat and add oil. When the oil is warmed, carefully add the floured meat to the pot and brown, about 5 minutes. Turn the meat over and brown, for an additional 5 minutes. Remove the meat and set aside on a plate.
Add the carrots, celery, onions and garlic and cook until the onions soften, about 7-8 minutes. (If you partially cover with the lid, the vegetables will soften more quickly.) Pour the beef broth and wine into the pot stirring to loosen up all the stuck-on browned bits. Finish by adding the neck meat back into the post along with the tomato paste and 2 bay leaves.
Cover with the lid, leaving just a small opening to allow for the steam to release while cooking. Carefully place the pot in the oven and cook for 6-7 hours. The longer you braise the meat the more time it will have to breakdown all the connective tissues that run throughout the neck. Baste the meat every two hours during the cooking time. You may find that you need to add more liquid if needed. During the last 30 minutes of cooking, add a whole cinnamon stick to the pot.
Carefully remove the meat from the pot and shred on a cutting board. Serve the braised venison over mashed potatoes and cover with the gravy. Garnish with diced green onions and parsley.