03Roast turkey 1 hour; baste with any pan juices. Reduce oven temperature to 350°F. Roast turkey 45 minutes. Pour 3/4 cup apple cider over; turn pan around. Continue to roast turkey until instant-read thermometer inserted into thickest part of thigh registers 165°F, basting and turning pan occasionally for even cooking, about 11/4 hours longer. Transfer turkey to platter; tent loosely with foil and let rest 30 to 45 minutes (internal temperature will rise 5 to 10 degrees).
04Pour all pan juices into large measuring cup. Spoon off fat that rises to surface. Transfer 2 tablespoons fat to heavy large saucepan; discard remaining fat. Place turkey roasting pan over 2 burners. Add 2 cups stock or broth and 3/4 cup cider. Bring to boil over high heat, scraping up browned bits. Boil liquid until reduced to 1 1/2 cups, about 6 minutes. Add mixture from roasting pan to degreased pan juices. If necessary, add enough stock to measure 3 1/2 cups stock mixture.
05Place saucepan with turkey fat over medium-high heat. Add flour; whisk 2 minutes. Whisk in stock mixture. Boil until gravy thickens enough to coat spoon thinly, about 6 minutes. Whisk in 2 tablespoons Calvados, or more to taste, and sage. Season with salt and pepper.