For the brine, whisk together the warm stock and salt until dissolved in a large, plastic food-storage bag set in a large bowl for stability. Add in cider, peppercorns, bay leaves and chops, and brine overnight.
Preheat oven to 375°F.
Heat large, cast-iron skillet over medium heat with a tablespoon of oil. Add onions and cook to light caramel in color, 15 minutes. Add apple and toss 2-3 minutes to tender-crisp; remove from pan and return pan to stove. Add remaining oil, 2 turns of the pan, and heat over medium-high heat. Pat chops dry, add to pan and brown 2-3 minutes on each side, brown bone-in edge as well. Transfer skillet to oven to finish cooking the chops through, 5-6 minutes. Douse pan with a touch of stock or a little apple brandy.
Meanwhile, cook sweet potatoes in boiling salted water to tender. Drain and return to hot pot. Add stock and butter, combine and season with salt, pepper and nutmeg to taste. Wilt in greens with spatula.
Top chops with onions and apples, a spoonful of pan juices and serve mashed sweet potatoes and greens alongside.