In a medium bowl, whisk together the buttermilk, egg, ½ tsp salt, pepper, ½ tsp paprika, onion powder, garlic powder, and pickle juice. Add the chicken and toss to coat. Cover and place in the refrigerator. Marinate for at least 30 minutes, or up to 4 hours.
In a shallow bowl, whisk together the flour, cornstarch, remaining ½ tsp salt, and remaining ½ tsp paprika.
Pour oil into a deep pan or pot, about 2–3 inches deep, and heat to 350°F. You'll know it's ready when a small bit of batter dropped in sizzles immediately.
While the oil is heating, remove the chicken from the marinade, letting the excess drip off. Dredge each piece in the flour mixture, pressing firmly to create a thick coating.
Fry in batches for 5–6 minutes, flipping halfway through, until golden brown and cooked through. Transfer to a wire rack set over a paper towel-lined baking sheet to keep crispy.
In a small bowl, melt the butter. Then, in a large bowl, whisk together the melted butter and buffalo sauce.
Add the fried chicken to the sauce and gently toss to coat. Serve immediately, garnished with parsley if desired.