Heat a large skillet over medium-high heat with the butter. Add the apple slices, cinnamon, and ½ teaspoon sage and fry and stir for 3 to 5 minutes or until the apples are softened, but still firm. Set aside to finish later.
PREPARE THE PORK:
Lay the tenderloins parallel to each other so the thin end of one is next to the thick end of the other. That way, when you tie the two pieces together, you will end up with a roast of equal thickness. Using the heel of your hand, gently press the tenderloins to flatten them a bit. Combine the remaining sage, salt and pepper and sprinkle some of it over the up side of each tenderloin, then place two layers of apples to cover one of the tenderloins. Place the other tenderloin on top, so that the apples are sandwiched the two roasts then tie with butcher's twine (or string) at 2-inch intervals. Sprinkle the rest of the sage seasoning mix all over the tied roast.
Heat the oil over medium-high heat in a large oven-proof skillet. Add the tied tenderloin roast and brown on all sides, about 5 minutes total. Insert pan into the oven and roast for 15 minutes or until it reaches an internal temperature of 140°F. Transfer the roast to a heated platter and cover loosely with foil while you make the apple pan sauce.
FINISH THE SAUCE:
Place the roasting pan over a medium burner and add the shallots. Fry for 1 minute, then add wine, chicken stock, and cider. Stir, scraping up any browned bits from bottom of the pan. Add reserved apple slices and any juices to the pan. Bring to a boil, and cook until the sauce just begins to thicken and become syrupy. Pour in the cream and cook a few minutes more until the sauce just thickens. Season to taste with salt and pepper.
Remove the twine from the roast and slice into 1-inch thick slices. Spoon sauce and apples over the slices and serve.
Notes
*If preparing this recipe as gluten-free, just be sure to use chicken broth and apple cider that is free of gluten.