Special equipment: kitchen twine
For the turkey: Place the turkey in a large bowl or pot, add the hard apple cider and salt. Then cover and refrigerate in the brine overnight.
For the stuffing: In a large skillet set over medium heat, melt the butter, then add the celery and onions, and saute until soft, 6 to 8 minutes. Add the calvados, apricots, dates, salt and pepper. Stir and cook at a simmer until the liquid reduces and thickens, and the fruit is plump, about 5 minutes.
In a large bowl, add the toasted bread, broth, pecans, sage, thyme and eggs. Add the vegetable mixture to bowl and mix to incorporate. Refrigerate until ready to use.
Preheat the oven to 375 degrees F. Grease a casserole dish.
Drain the turkey from the brine, rinse and pat all over to dry. Lay the turkey skin-side down on a work surface and use a sharp knife to butterfly the breast so that it lays flat. Sprinkle the turkey with 2 tablespoons of the Poultry Seasoning, then place 3 cups of the stuffing in the center of the breast and fold the ends of the turkey to cover. Flip the turkey over to seam-side down, and use kitchen twine to tie the turkey at 1-inch intervals.
Place the remaining stuffing in the prepared casserole dish, and set aside.
Arrange the sliced onions in the center of a roasting pan. Rub the turkey skin with the butter, sprinkle with the remaining 2 tablespoons Poultry Seasoning, and then place the turkey over the sliced onions. Roast, basting occasionally, until the internal temperature reaches 160 degrees F on an instant-read thermometer, about 2 hours.
After about 1 hour 30 minutes, add the stuffing to the oven and bake until golden brown, about 30 minutes.
Remove the turkey from the pan and rest for 10 to 15 minutes, reserving the pan with the drippings for a later use.
For the gravy: Place the roasting pan with the drippings on the stovetop set over medium-high heat. Pour in the wine to deglaze the pan. Use a spoon to scrape the bits from the bottom of the pan.
In a medium bowl, add 1/4 cup of the chicken broth and the flour. Whisk to make a slurry.
Add the remaining 1 cup chicken broth and the slurry into the roasting pan. Whisk until combined and smooth. Then simmer until the gravy reduces and thickens, 5 to 10 minutes.
Remove the strings from the turkey and carve it into slices. Serve the turkey with the stuffing and gravy.
Place the marjoram, parsley, sage, rosemary and thyme in a spice grinder or blender and grind until powdery.