Combine the bone-in chicken pieces with buttermilk and hot sauce, then soak for at least 30 minutes or overnight, fully submerging as best as possible. Keep it in the refrigerator during soaking for food safety, and pause when the chicken looks evenly coated with buttermilk.

Whisk all-purpose flour, garlic powder, onion powder, smoked paprika, cayenne pepper, salt, and cracked black pepper together in a shallow dish. Mix until the flour looks evenly speckled with spices.

Remove chicken from the buttermilk, letting excess drip off, then dredge firmly in the seasoned flour coating. Press to form a thick layer, and shake off loose flour.

Repeat the dip-and-dredge process by returning the chicken to any remaining buttermilk, letting excess drip off again, then dredging a second time in the seasoned flour coating. Stop when the coating looks rough and clinging thickly to the chicken.

Heat 2-3 inches of vegetable oil to 350°F in a large cast iron skillet. Wait until the oil holds a steady 350°F and looks shimmering before frying.

Fry chicken for 10-12 minutes per side, turning once when the coating is deeply golden. Cook until the internal temperature reaches 165°F and the crust looks firm and crisp.

Transfer fried chicken to paper towels to drain. Let it rest briefly so the coating sets and stays crunchy.

For the gravy, whisk pan drippings and flour in a skillet over medium heat for 1 minute. Stir constantly until the mixture looks smooth and slightly thickened.

Gradually whisk in whole milk and cook until thickened, keeping the mixture at a gentle simmer level. Continue whisking until the gravy coats the back of a spoon.

Season with salt and pepper to taste. Taste and adjust until the flavor is balanced without thinning the gravy.

Serve the chicken immediately with white gravy poured over the top. Pour generously so the gravy pools around the base while the chicken coating is still crisp.