Place the chicken pieces in a large bowl. Add salt, pepper, garlic, dried mustard, paprika, and sage. Stir to coat the chicken evenly. Pour the buttermilk over the seasoned chicken. Stir well to coat the chicken.
Refrigerate this mixture for at least 1 hour, but the longer you marinate, the more tender it will be. It may be left overnight as well.
In a shallow dish, whisk together the flour, baking powder, salt, garlic powder, paprika, basil, thyme, onion powder, and cayenne pepper.
Heat the oil to about 340°F. You want to be able to fry the outside to a crisp golden brown without burning while still cooking the chicken all the way through!
Remove each piece of chicken from the marinade, put it into the shallow dish with the flour mixture and toss. Make sure the whole surface of each piece of chicken is coated very well.
Place the chicken pieces into the oil. You may cook 4 or 5 pieces at a time, but don’t crowd the chicken. Turn as necessary and fry until golden brown. It will take about 15 minutes for each piece to cook. Make sure each piece is fully cooked - the internal temperature should be 170°F. I recommend keeping a candy thermometer in the oil as you cook, the temperature might crop some as you place in the cold chicken so you will need to adjust the heat according to stay around 340°F.
Allow the chicken to drain on a wire rack to help the chicken stay crispy.