In a very large/tall stockpot, add all brine ingredients, except for ice and water. Heat over high heat* and stir until dissolved. Allow to cool.

Gently submerge turkey into the brine. Cover the top with ice. Pour in enough cold water to completely submerge turkey in liquid. Stir the liquid to combine. Store in fridge or cool location (below 40F). Swirl/stir a couple of times during brine time – 48 hours recommended, but 24 hours minimum.

Drain and place turkey upright on roasting pan’s wire rack to fully drain for several hours and allow it to reach room temp. Pat dry turkey skin thoroughly with paper towels.

Preheat oven to 450F, with rack on a lower position. Combine dry rub ingredients in bowl. Gently spread one-third of the dry rub between skin and flesh throughout entire bird, taking care not to rip the skin. Sprinkle and press remaining dry rub on outside of skin throughout entire bird. Seal together loose skin of neck area with toothpicks.

Bring 1 cup water to a boil in a small pot. Remove from heat and add apples, 1 quartered onion, cinnamon stick, rosemary, and sage and let steep for 1 minute. Dispose of water and insert the steeped aromatics into the turkey cavity.

Add 1 quartered onion, carrots, and celery to the bottom pan of a turkey roaster. Place sheet of foil onto the roaster's wire rack and poke holes in the foil to allow juice to flow through. (The foil keeps the bird from sticking to the rack and makes it much easier to flip halfway through the cooking process.) Place turkey breast-side down on the foil-lined rack.

Roast for 1 hour at 450F. Drop heat to 300F and roast for another 30 min. Remove turkey from oven and carefully flip it over, breast-side up. Insert meat thermometer into center of turkey breast and return to oven. Continue roasting until meat thermometer registers 160F.

Transfer rack with turkey to cutting board, tent with foil, and let it rest – do not cut into it, nor remove the thermometer probe for at least 15 minutes. Set roasting pan with roasted vegetables and pan drippings aside for later.

While turkey is roasting, heat 2 TB oil in a large pot. Add giblets/neck to hot oil and sear until well-browned. Remove neck and set aside. Throw out giblets.

Add remaining 2TB oil to the pot and heat until almost smoking. Add garlic and sauté until golden brown. Add onions, carrots, and celery, cooking until onions become translucent. Add water and bring to a boil.

Add neck back in and boil over heat. Continue to boil until liquid is reduced by about half. Keep warm.

Place the turkey roasting pan with roasted vegetables over two stovetop burners. Pour reduced gravy with veggies into the roasting pan and bring to a boil. Use spatula to loosen all brown bits from bottom of roasting pan. Boil and reduce by at least half again, or until gravy has the desired flavor strength. It should taste amazing when it's done!

Strain mixture so you are left with just the au jus. Skim fat off the top and serve with sliced turkey.