Load the slow cooker. Add the chicken, ranch mix, onion soup mix, and pepperoncini (plus juices) to the basin of a crockpot. Give everything a stir and arrange the slices of butter over the chicken.
Cook. Cook on Low for 7 hours or on High for 4 hours.
Shred. Shred the chicken inside the crockpot using two forks or shredder claws to pull the meat apart.
Serve. Serve your Mississippi chicken warm over mashed potatoes or cooked white rice.