Pat chicken thighs thoroughly dry with paper towels on both sides. Dry skin is essential for developing a shattering, crackling crust. Season evenly with olive oil, kosher salt, black pepper, garlic powder, and smoked paprika.

Heat a large heavy cast-iron skillet over medium heat. Place chicken thighs skin-side down in the dry skillet (their natural fat will render quickly). Cook undisturbed for 8 to 10 minutes until the skin is deep golden-brown and intensely crisp. Flip and cook for 3 to 4 minutes on the flesh side. Transfer chicken to a clean plate, leaving 1 tablespoon of rendered chicken fat in the skillet.

Add sliced apple wedges to the skillet and sear for 2 minutes per side until lightly caramelized. Add minced garlic and cook for 30 seconds until fragrant. Push apples to the side.

Pour in the unfiltered apple cider, honey, Dijon mustard, apple cider vinegar, rosemary sprigs, and thyme. Bring to a rapid rolling boil over medium-high heat. Simmer vigorously for 6 to 8 minutes, stirring frequently, until the liquid reduces by two-thirds into a syrupy, glossy amber glaze that coats the back of a spoon.

Swirl butter into the bubbling reduction until melted and glossy. Return chicken thighs to the skillet skin-side up. Spoon the hot, sticky glaze repeatedly over the chicken for 2 to 3 minutes until an internal meat thermometer registers 165°F (74°C). Garnish with fresh rosemary and caramelized apples, and serve piping hot.