Place the chicken breasts in the bottom of the slow cooker in an even layer.

Sprinkle the ranch seasoning mix and au jus gravy mix evenly over the chicken, then top with the sliced butter, whole pepperoncini peppers, and pepperoncini brine.

Cover and cook on low for 6 hours, or until the chicken is very tender and easily shreds with a fork.

Shred the chicken directly in the slow cooker using two forks, then stir it well into the buttery juices.

Let the shredded chicken sit in the sauce for 5 minutes to absorb more flavor, then serve warm over mashed potatoes, rice, or on sandwich buns with parsley if desired.