Place your bone-in chicken pieces inside a large gallon-sized Ziploc bag, pour the 2 cups of buttermilk and 1 tablespoon of kosher salt directly over the meat, and seal tightly. Massage the bag for 30 seconds to dissolve the salt crystals, then transfer it to the refrigerator to marinate for a minimum of 4 hours or up to 24 hours.

Two hours before cooking, pull the chicken bag from the refrigerator and let it sit undisturbed on the counter. Allowing the meat to drop down to a uniform room temperature is essential; dropping ice-cold chicken directly into boiling oil causes the pan temperature to plummet instantly, which leaves you with a heavy, grease-logged crust and raw meat near the bone.

In a large, shallow baking dish, whisk together the all-purpose flour, cornstarch, garlic powder, onion powder, smoked paprika, cayenne pepper, sea salt, and black pepper until completely unified. Take 4 tablespoons of the liquid buttermilk marinade straight from the chicken bag, drizzle it evenly over the seasoned flour, and use your fingers to rub it in until small, pea-sized dough clumps form throughout the breading.

Set a deep cast-iron skillet or a heavy-bottomed Dutch oven over medium-high heat and fill it with neutral oil to a depth of 2.5 inches. Heat the oil until a deep-fry thermometer reads exactly 350°F to 360°F.

Lift a piece of chicken from the buttermilk brine, letting the heavy excess drip away, and drop it straight into the lumpy flour mixture. Use the palms of your hands to aggressively press and squeeze the flour into the meat, ensuring the shaggy dough bits completely anchor onto all sides of the chicken skin, then gently shake off any completely loose powder.

Lower 3 to 4 pieces of the dredged chicken away from you into the hot oil, ensuring you do not overcrowd the pan. Let the chicken fry undisturbed for exactly 2 minutes without touching it, which gives the wheat starches time to set, expand, and cleanly bond with the chicken proteins before you move them around.

Maintain the oil heat steadily at 300°F to 325°F while frying, flipping the pieces occasionally with metal tongs. Cook the chicken for 8 to 10 minutes until the exterior crust turns a deep, shaggy mahogany golden brown and a meat thermometer inserted into the thickest part near the bone registers a safe 165°F for white meat or 175°F for darker cuts.

Lift the hot chicken out of the pan using a slotted spoon or metal spider and place the pieces directly onto a raised wire cooling rack set over a rimmed baking sheet. Letting the fried chicken drain flat on a wire rack allows fresh air to circulate underneath the meat, which wicks away surface oil instantly and preserves a perfectly shatter-crisp bottom crust instead of letting it sit and turn soggy on a paper towel. Let it rest for 10 minutes to trap the internal juices before serving.