For the Brining:
Frank McClelland's Thanksgiving turkeys come straight from the farm; his usual meal preparation is a multi-step production involving homemade stock and homemade basting liquid, along with the usual gravy and dressing. We've streamlined that process a bit, but our version still features the wonderfully moist meat you get from brining, plus many layers of apple, herb, spice, and Madeira flavors.
Rinse turkey thoroughly under cold water. Trim excess fat and discard. Set aside.
In a large pot (at least 8 quarts) over high heat, stir together cider, vinegar, and brine seasonings. Warm brine until sugar and salt dissolve, about 5 minutes. Remove from heat, add 1 quart ice water, and cool to room temperature.
If your pot is large enough (and your refrigerator can accommodate it), put turkey in brine and refrigerate 12-24 hours. Otherwise, double-bag two plastic roasting bags and set them, openings up, into your roasting pan. Add turkey and pour brine in carefully. Close bags securely with tight knots or twist ties, and transfer pan to refrigerator for 12-24 hours, turning the turkey once during that time to make sure all parts are properly brined. When you're ready to roast, remove bird from brine and pat dry. Discard brine.
For the Roasting:
Preheat oven to 450°. Stuff turkey cavity with Sausage-Currant Brioche Dressing. Tie turkey legs together with kitchen twine.
In a small bowl, stir together butter and sage. Use your fingers to separate breast meat from skin and stuff butter under skin. Rub skin all over with olive oil, and sprinkle with salt and pepper.
Place turkey in roasting pan, breast side up. Pour broth (or stock) and Madeira into bottom of pan. Roast bird 30 minutes; then reduce heat to 350º. Insert a probe into the thickest part of the breast to monitor temperature.
Basting turkey every 20 minutes, roast until thermometer registers about 160º and leg joints feel loose, 2-2-½ hours longer for a 15-pound bird. If you like, you may bring the oven temperature up to 425º for the final 20 minutes of cooking to enhance browning.
Remove turkey from pan and cover with foil; let sit 30 minutes before carving. Reserve pan juices and and use them to make Madeira Gravy (see accompanying recipe, below). Serve turkey with dressing and gravy.
Sausage-Currant Brioche Dressing
In a small bowl, stir together currants and Port. Set aside. Meanwhile, in a 4- to 5-quart pot over medium-high heat, melt butter. Add sausage and cook, stirring and breaking up pieces with a wooden spoon, until browned, about 10 minutes. Add onions, celery, salt, and pepper; cook, stirring, until translucent, about 6 minutes. Add garlic, orange zest, sage, and nutmeg; stir. Add bread cubes and broth (or stock).
Drain currants, discarding Port, and add to dressing. Stir to combine ingredients evenly. Remove from heat and cool to room temperature. Bake in a greased 9x13-inch baking dish at 400º for 40 minutes, or chill in refrigerator and proceed with turkey recipe.