Marinate the Chicken: Add the chicken pieces to a large resealable bag or large bowl.
In a mixing bowl, whisk together the buttermilk, pickle juice, kosher salt, and black pepper. Pour over the chicken, making sure all pieces are fully coated.
Refrigerate for at least 3 hours or up to overnight.
Remove the chicken from the refrigerator 30-45 minutes before frying to take the chill off. This helps the chicken cook more evenly.
Prepare the Coating: In a large shallow bowl, whisk together the flour, cornstarch, baking powder, salt, paprika, black pepper, garlic powder, onion powder, cayenne, and white pepper.
Place a wire rack over a baking sheet nearby.
Dredge the Chicken: Remove one piece of chicken from the marinade, allowing the excess to drip off slightly.
Coat thoroughly in the flour mixture, pressing the flour into every crevice for lots of crispy texture.
Place the coated chicken on the wire rack and repeat with the remaining pieces.
Pour a little of the reserved buttermilk marinade into a separate bowl.
Working one piece at a time, dip the chicken lightly back into the buttermilk, then dredge again in the flour mixture for a second coating.
Return the chicken to the wire rack.
Let the chicken rest for 15-20 minutes before frying. Dont skip this step!
Heat the Oil: Add enough oil to a large cast iron skillet to come about halfway up the chicken pieces, usually about 1 to 1½ inches deep.
Heat the oil over medium-medium high heat until it reaches 350°F.
Try to maintain the oil temperature between 325°F and 350°F while frying.
Fry the Chicken: Carefully place a few pieces of chicken into the hot oil, skin-side down first. Do not overcrowd the skillet.
Fry until deeply golden brown and crispy, turning occasionally for even browning. Smaller drumsticks may take around 12-14 minutes total, while larger thighs can take 16-18 minutes.
The chicken is done when the thickest part reaches 165°F on an instant-read thermometer.
If the crust is browning too quickly before the chicken is cooked through, lower the heat slightly.
Transfer the fried chicken to a clean wire rack and allow it to rest for 5 minutes before serving. Resting keeps the crust crispier than draining on paper towels.
Serve hot.