Using a cooler or a 5-gallon food-safe bucket combine hot water with kosher salt and sugar as directed above. Add ice water and stir until combined and quite cold. Add the turkey, cover and chill for 8 to 10 hours. If using a cooler, make sure to add additional ice or frozen reusable ice packs to keep the turkey about 35°F.

(FYI - Make sure to place the ice packs in a sealable plastic bag before placing in the brine so there's no chance of the ice pack rupturing and contaminating the turkey.)

Place the turkey neck in a medium saucepan and cover with chicken stock or water. Coarsely chop 1 stalk of the celery, 1 onion, and 1 carrot; add to the stock. As you prepare the remaining vegetables, add the stems and skins to the saucepan. Bring to a boil over high heat. Reduce the heat to simmer and cook until fragrant and flavorful, about 1 hour.

Heat oven to 425°F, place oven rack in lowest position. Remove the turkey from the brine and rinse inside and out with cold running water. Pat dry and season turkey inside and out with freshly ground pepper. Place remaining celery and onion, apple, parsley, thyme, sage, rosemary, and bay leaf in cavity. Working from large cavity end, run fingers between skin and flesh of breast to loosen skin without tearing. Put 2 tablespoons butter under skin and spread butter evenly. Tie drumsticks together with kitchen string and fold wings under the body. Place the turkey on rack in a large roasting pan. Add 1 cup of the stock to the roasting pan. Brush remaining 2 tablespoons butter over turkey, roast 30 minutes. . Reduce oven temperature to 350°F. Baste turkey with pan drippings and continue roasting, basting every 30 minutes, until a thigh registers 165°F on a thermometer, and additional 2 to 2 1/2 hours.

Carefully tilt turkey to release any juices from inside cavity into roasting pan. Transfer turkey to serving platter. Discard celery, apple, parsley, thyme,  sage, rosemary, bay leaf and onion from cavity. Allow turkey to rest 30 minutes before carving. Serve with Apple Cider Gravy.