In a large mixing bowl, add the chicken, buttermilk, pickle juice, egg, and seasonings. Mix to combine, cover with plastic wrap and refrigerate for 1-2 hours or overnight.
In a separate large mixing bowl, make dredging mixture by whisk together the flour, cornstarch, baking powder and seasonings.
Double coat the marinaded chicken pieces one at a time by first coating in flour mixture, then dipping the entire chicken into the marinade (wet batter) and lastly back into the flour mixture. You want to make sure that the chicken is entirely coated in the flour mixture. Transfer to a parchment lined baking sheet and let rest for 10 minutes. Preheat oven to 200F.
Heat oil to 350F in a pan or skillet over medium high heat. In batches, fry the chicken pieces until crispy and golden brown, about 4-5 minutes per side. The internal temperature of the chicken should be at least 165F. Transfer fried chicken to a wire rack placed over a parchment lined sheet pan.
Once all chicken pieces are done frying, transfer sheet pan to the oven to keep chicken warm as the sauce is prepared.