Place chicken thighs in the bottom of the slow cooker.
Sprinkle the ranch dressing mix evenly over the chicken.
Sprinkle the au jus gravy mix over the ranch dressing.
Place the pepperoncini peppers on top of the chicken.
Cut the butter into slices and place over the chicken and peppers.
Cover the slow cooker with the lid.
Set the slow cooker to low and cook for 4 hours.
After cooking, shred the chicken in the slow cooker with two forks.
Stir the sauce until well combined with the shredded chicken.
Serve hot, garnished with fresh parsley.