2 cups whole, cultured buttermilk
3 tablespoons kosher salt
4 pounds skin-on, bone-in chicken breasts, cut in quarters
2 pounds skin-on, bone-in chicken legs, cut into drumsticks and thighs
2 cups flour
2 teaspoons ground cayenne pepper
1 quart vegetable oil
1. Marinate: Pour 1 cup buttermilk and 1 1⁄2 teaspoons salt into each of two 1-gallon zip-top bags. Add half the chicken pieces to each, seal, and shake to coat. Refrigerate 2 hours to 2 days.
2. Dredge: Whisk flour with remaining 2 tablespoons salt and the cayenne in a pie plate. Dredge chicken.
3. Fry: Heat oil to 350 degrees in a cast-iron skillet. Add half the chicken, avoiding spatter, and fry until golden on one side, 10 minutes. Turn and fry until golden, juices run clear, and chicken reaches 165 degrees inside, about 10 mintues more. Drain on a rack. Return oil to 350 degrees. Repeat with remaining chicken.