Preheat the oven to 400°F. Pat the chicken pieces dry and place them in a gallon-size zip-top bag. Pour the buttermilk over the chicken, seal the bag, and turn the pieces until they are evenly coated. Set aside while you prepare the breading.
In a separate gallon-size zip-top bag, combine the breadcrumbs, flour, garlic powder, onion powder, parsley, paprika, salt, black pepper, and cayenne, if using. Seal the bag and shake until everything is evenly combined.
Line a large baking sheet with parchment paper or foil. Stir the melted butter and oil together, then pour half of the mixture onto the baking sheet. Use a pastry or basting brush to spread it into an even layer.
Working with one piece at a time, remove the chicken from the buttermilk and let the excess drip off. You want just a thin coating of buttermilk so the breading sticks without becoming too thick or soggy.
Place one piece of chicken at a time in the bag with the breadcrumb mixture. Seal the bag and shake until the chicken is completely and evenly coated.
Place the coated chicken on the prepared baking sheet and repeat with the remaining pieces. Leave some space between each piece so the chicken bakes evenly and the coating can get crispy.
Drizzle the remaining butter and oil mixture evenly over the coated chicken. Bake for 20 minutes.
Carefully turn each piece over and bake for another 20 to 25 minutes, or until the coating is golden and the thickest part of the chicken reaches 165°F. Boneless pieces may cook faster, so start checking them earlier. Let the chicken rest for about 5 minutes before serving.