Add the chicken to the slow cooker.
Sprinkle on the au jus mix, and ranch seasoning, then top with butter and pepperoncini.
Cook on LOW for 3 hours, or on HIGH for 1.5 or 2 hours. When the chicken is ready, check for doneness by inserting the thermometer in the center of the chicken, and the internal temperature of the chicken should read 165°F or 75°C.
Let the chicken rest for 5 minutes, then shred it while it's still warm using a hand mixer, 2 forks, or your hands.
Serve over mashed potatoes, pasta, or rice. To make sandwiches, serve on rolls or toasted buns with provolone cheese.