Step 1

Bring 2 cups water to a boil in a medium saucepan. Add kosher salt, sugar, juniper berries, peppercorns, halved head of garlic, and 1 thyme sprig; stir to dissolve salt and sugar. Transfer to a medium bowl and add 5 cups ice cubes. Stir until brine is cool. Add pork chop; cover and chill for at least 8 and up to 12 hours.

Step 2

Preheat oven to 450°. Set a wire rack inside a rimmed baking sheet. Remove chop from brine; pat dry. Heat oil over medium-high heat in a large cast-iron or other oven-proof skillet. Cook chop until beginning to brown, 3-4 minutes. Turn and cook until second side is beginning to brown, about 2 minutes. Keep turning chop every 2 minutes until both sides are deep golden brown, 10-12 minutes total.

Step 3

Transfer skillet to oven and roast chop, turning every 2 minutes to prevent it from browning too quickly, until an instant-read thermometer inserted horizontally into center of meat registers 135°, about 14 minutes. (Chop will continue to cook during basting and resting.)

Step 4

Carefully drain fat from skillet and place over medium heat. Add butter, 2 unpeeled garlic cloves, and remaining thyme sprig; cook until butter is foamy. Carefully tip skillet and, using a large spoon, baste chop repeatedly with butter until butter is brown and smells nutty, 2-3 minutes.

Step 5

Transfer pork chop to prepared rack and let rest, turning often to ensure juices are evenly distributed, for 15 minutes. Cut pork from bones, slice, and sprinkle with sea salt.