In a small bowl, whisk together all of the seasoning ingredients. Reserve half of the spice mix (eyeball it) for the marinade (Step 2) and set aside the rest to use in the coating.
In a large bowl, whisk together the buttermilk, kosher salt, and half of the prepared spice mix. Add the chicken and toss to coat. Marinate the chicken in the refrigerator for 8 hours or overnight.
Preheat the oven to 400 degrees F.
Line a baking sheet with aluminum foil. This will help with easy clean up. Place a metal cooling rack over the baking sheet and spray or brush well with olive oil.
Remove the chicken from the fridge and reserve 1 ½ Tablespoons of the marinade.
Beat the egg in a shallow baking dish (I like to use a pie plate). Take another shallow dish and combine the flour, arrowroot, baking powder, remaining spice mix and 1 teaspoon of salt.
Drizzle the reserved marinade (1 ½ tablespoons) over the flour mixture and toss it together with your fingertips to create some lumps.
To assemble: take the chicken breasts, one at a time, and dip into the egg mixture, coating both sides, then dredge with the flour mixture. Press the chicken into the flour mixture to help it adhere and toss to coat both sides. Transfer coated chicken pieces to the prepared cooling rack.
Coat the top of the chicken with a little olive oil. You can either brush with oil or spray it with oil. Be sure to lightly coat the entire top of the chicken or you’ll be left with dry flour spots.
Bake in the oven for 25-30 minutes or until a thermometer inserted into the thicket part reads 160 degrees. Optional step: set oven to broil and broil chicken pieces about 6 inches from heat source for 2-3 minutes or until chicken is nicely browned.