Prosciutto-Wrapped Pork Loin with Roasted Apples

Ingredients:
1 ounce (1 cup) dried whole porcini mushrooms
2 ounces (3/4 cup) dried apples
1 pound kale, bottom stems trimmed
2 teaspoons kosher salt plus more
2 tablespoons (1/4 stick) unsalted butter
1 cup minced onion
1 tablespoon finely minced garlic
1 1/2 teaspoons dried thyme
1 1/2 teaspoons dried rosemary
2 tablespoons brandy or Calvados
1/2 teaspoon freshly ground black pepper
1 pound ground pork
1 (trimmed) 2 1/2-3 pound pork loin
1 teaspoon kosher salt plus more for seasoning
1/2 teaspoon freshly ground black pepper plus more for seasoning
3 ounces thinly sliced prosciutto
5 sprigs rosemary
4 medium apples (such as Granny Smith or Fuji), quartered, or 8 small apples, halved
3 tablespoons unsalted butter, divided
2 tablespoons extra-virgin olive oil
1 cup dry hard cider
1/2 cup low-salt chicken stock
Ingredient info: Dried porcini are available at better supermarkets and at specialty foods stores and Italian markets.

Instructions:
Place dried mushrooms and dried apples in separate small bowls. Add 1 cup boiling water to each bowl. Let mushrooms and apples soak until very soft, about 30 minutes. Strain mushrooms. Cover and chill soaking liquid (about 3/4 cup). Drain apples, discarding soaking liquid. Finely chop mushrooms and apples, combine in a small bowl, and set mushroom and apple mixture aside.
Meanwhile, blanch kale in boiling salted water just until wilted, about 1 minute. Using tongs, transfer kale to a rimmed baking sheet. Refrigerate until cool. Remove any large, tough ribs.
Melt butter in a large skillet over medium heat. Add onion; cook, stirring often, until soft and lightly golden, about 8 minutes. Add mushrooms and apples; cook, stirring occasionally, until flavors meld, about 5 minutes. Stir in garlic, thyme, and rosemary; cook for 1 minute. Add brandy and cook until liquid is absorbed, about 1 minute. Stir in 2 teaspoons salt and 1/2 teaspoon pepper. Transfer mixture to a bowl and let cool completely. Add ground pork and stir to combine well.
To butterfly, put pork loin on a work surface with short end facing you. Holding a long, thin sharp knife parallel to work surface and beginning along one long side, cut 1/2" above underside of roast. Continue slicing inward, pulling back the meat with your free hand and unrolling the roast like a carpet, until the entire loin is flat. Cover with a sheet of plastic wrap. Using a meat mallet, pound to an even thickness.
Uncover pork. Season with 1 teaspoon salt and 1/2 teaspoon pepper. Place kale leaves on top of loin in an even layer, overlapping as needed and leaving a 1" border. Spread filling on top of kale. Roll pork into a tight cylinder. Wrap one layer of prosciutto around roast. Tie roast securely with kitchen twine in 1" intervals. Tuck rosemary sprigs under twine, spacing apart. DO AHEAD: Pork roast can be made 1 day ahead. Cover and chill. Let stand at room temperature for 1 hour before continuing.
Preheat oven to 400°F. Place apples in a roasting pan. Melt 1 tablespoon butter with oil in a large skillet. Brown pork on all sides, about 5 minutes total, then set on top of apples in pan. Add cider and 1/2 cup water to skillet and bring to a boil, scraping up browned bits. Pour mixture into roasting pan. Roast pork until an instant-read thermometer inserted into center of loin registers 140°F (it will be cooked medium but still slightly pink), about 1 hour 40 minutes. Let roast rest for at least 20 minutes and up to 2 hours.
Put roast on a platter. Reserve apples from roasting pan; spoon off fat from juices in pan. Place pan on top of stove over medium-high heat. Add chicken stock. Pour in reserved mushroom liquid, leaving any sediment behind, and cook, scraping bottom of pan to release any browned bits, until slightly thickened, about 5 minutes. Whisk in remaining 2 tablespoons butter and season to taste with salt and pepper. Strain sauce; slice pork. Serve sauce and apples alongside sliced pork.