1
Preheat the oven to 375° F.
2
Butterfly the roast (see tips below).
3
Heat the oil and butter in a large skillet over medium high heat. Add the celery, carrots, and onions and cook until softened, about 5 minutes.
4
While the vegetables are cooking, combine the eggs, milk, salt, and pepper together and whisk until well combined. Mince sage and rosemary.
5
Place the bread in a large bowl and combine with the vegetable mixture, liquid ingredients, apples, sage, and rosemary. Toss together gently until the bread has absorbed most of the liquid.
6
Cut 3 pieces of butcher’s twine about 4 inches longer than the longest side of the butterflied roast. Lay the string on a cutting board horizontally, and lay the roast on top of the string to cover the pieces of string.
7
Place half of the stuffing mixture onto the butterflied pork loin and press it down firmly. Roll the roast up and tie with the butcher’s twine to hold the roast together, taking care not to tie it too tightly, and press any stuffing that comes loose back into the ends of the roast.
8
Place the stuffed and tied roast, fat cap up, on a rack over a baking sheet. Season liberally with salt and pepper and roast until a meat thermometer inserted into the roast registers 140° F, about 75 to 90 minutes.
9
Place the remaining stuffing in a small ovenproof casserole dish and cover with foil. After the roast has been in the oven for 30 minutes, place the extra stuffing in the oven to cook alongside the roast.
10
Remove the foil from the extra stuffing and remove the roast from the oven. Allow it to rest for 10 minutes and then remove the extra stuffing from the oven.
11
Cut the twine from the roast and discard it, and then cut the roast into 6 thick slices, taking care not to lose the stuffing when you slice it. Serve with the extra stuffing on the side and your favorite gravy.