If your turkey is frozen, allow 2 to 3 days for it to fully defrost in the refrigerator. Remove innards. Prepare brine at least 1 day ahead of roasting turkey so it can soak in the brine overnight.
For the brine:
In a large pot over medium-high heat, combine salt, brown sugar, vegetable stock, peppercorns, rosemary, bay leaves and cinnamon stick. Bring to boil and stir until sugar has dissolved. Remove from heat and allow to cool. Refrigerate until ready to use.
In a large bucket, combine brine and ice water. Submerge turkey in brine, breast side down. If turkey floats in brine, weigh it down with a plate so it is fully submerged. Cover and refrigerate overnight, or 8-12 hours.
Adjust oven racks to lowest position and preheat oven to 425°F. Remove turkey from brine and rinse inside and out with cold water. Discard brine (be sure to clean out your sink well after this step!). Place turkey breast side up in roasting pan with rack, or on a roasting rack in a sheet pan. Pat dry with paper towels.
For the aromatics:
Stuff turkey with apple, onion, cinnamon stick, rosemary, sage and thyme.
For the herb butter:
In small bowl, combine butter, fresh herbs and garlic. Season generously with salt and pepper. Stir together with spoon until well blended. Starting around the neck, run your hand between the skin and meat of turkey, gently separating them. Do the same from the other side of the bird, loosening the skin around thighs and legs. Now use about two thirds of the compound butter to rub over the meat, under skin of turkey. It is okay if the butter is clumped – it will melt as it cooks. Tuck wings under bird. Melt remaining butter in microwave and brush in an even layer over skin of bird, breast side up in roasting pan.
Transfer pan to oven and cook at 425°F for 45 minutes. Reduce the oven temperature to 350°F and continue to roast until an instant-read thermometer inserted in thickest part of the breast registers 180°F when inserted into inner thigh and 170°F when inserted into breast. Monitor browning of skin and once it has reached the desired shade of golden brown, after about 60-90 minutes, tent loosely with foil through the remainder of the cooking time. A 14-16 pound bird will take approximately 2 to 2 1/2 hours. Once turkey is done and you have removed it from oven, loosely cover with foil and let it rest for 15 minutes before carving and serving.