Prep the crock pot. Lightly spray the insert with nonstick spray for easier cleanup.
This step is optional but helpful.
Layer the chicken. Place chicken breasts (or thighs) in a single layer. If they overlap slightly, that’s okay.
Add the seasonings. Sprinkle the ranch seasoning and au jus gravy mix evenly over the chicken. Add a few grinds of black pepper.
Top with pepperoncini. Scatter 6–10 pepperoncini over the chicken and splash in 1 to 2 tablespoons of the brine for extra tang.
Butter and broth. Dot the butter pieces over the top.
Pour in 1/4 cup chicken broth around the edges to prevent drying.
Cook low and slow. Cover and cook on Low for 4 to 6 hours or High for 2.5 to 3.5 hours, until the chicken is very tender and easily shreds.
Shred and toss. Shred the chicken right in the crock pot using two forks. Stir to coat with the sauce and let it sit on Warm for 10 minutes to soak up the juices.
Taste and adjust. Add more pepperoncini or brine if you want extra zing. If it’s too salty, stir in a splash of broth or a squeeze of lemon.
Serve. Spoon over rice or mashed potatoes, pile onto toasted rolls, or tuck into tortillas with a crisp slaw.