2 cups low-sodium turkey stock, chicken stock, chicken broth, or water, plus more as needed
1/4 cup all purpose flour
In a small bowl, mix together the kosher salt, 2 tablespoons of the light brown sugar, and the black pepper to form the dry brine mixture. Set aside.
One to two days before cooking your turkey, place it on a wire rack set over a rimmed baking sheet and pat dry all over with paper towels. Sprinkle and rub the dry brine mixture all over the turkey, including in the cavity. Place the turkey, uncovered, in the refrigerator for at least 8 hours, and up to 48. The longer the better. Make sure that the turkey isn’t touching anything.
When ready to cook, take the turkey out of the refrigerator for 30 minutes and then preheat the oven to 425°F. Do not rinse the turkey.
Stuff the cavity of the turkey with the apples, shallots, rosemary, and sage (reserving 4 sage leaves for later). Truss the turkey and transfer to a roasting pan. Roast for 45 minutes.
Meanwhile, chop the remaining sage. In a small saucepan, combine the chopped sage, apple cider, and remaining brown sugar. Bring to a boil, stirring occasionally, until the sugar is dissolved and the mixture is reduced to about 1/4 cup, about 10 minutes. Remove from heat and whisk in the butter, a bit at a time.
Remove the turkey from the oven and reduce heat to 350°F. Brush generously with the glaze. Return the turkey to the oven and continue to cook until a thermometer inserted to the thighs registers 170°F, brushing with glaze every 30 minutes. The total cook time should wind up being around 2 hours. If the wings or legs start to get too dark, cover them with small pieces of tinfoil.
Let the turkey rest for 30 minutes before carving and serving.
When the turkey is ready to serve, lift it from the roasting pan and place the roasting pan on the stove over medium heat. In a small bowl, spoon about 1/4 cup of the hot liquid into the bowl and whisk until a smooth paste forms. Then add a spoonful of the paste to the roasting pan and whisk until thickened with no lumps remaining, about 10 minutes. Make sure you’re scraping up the bits at the bottom of the pan. Add more of the flour paste as needed. Once thickened, you can whisk in additional stock, broth, or water, if desired.