Rinse chicken pieces and pat dry. Pour buttermilk in a shallow dish or bowl and add chicken pieces. Place in refrigerator and marinate overnight.
When ready to prepare, mix potato flakes, flour, poultry seasoning, salt, and pepper in a medium bowl. Dredge marinated chicken in potato/flour mixture to coat. Set aside for 15 minutes to allow coating to stick.
Heat oil in a deep-fryer or large saucepan to 350 degrees F (175 degrees C).
Fry chicken slowly over medium heat until golden brown and juices run clear.