To the basin of a 6 quart slow cooker, lay in the chicken breasts. Sprinkle the ranch seasoning over the top. Place the cubed cream cheese on top of the chicken. Cover and cook on LOW for 6 hours or HIGH for 4 hours. Once the chicken is cooked through, stir to distribute the cream cheese sauce, then use two forks to shred the chicken. Stir in the the crumbled bacon and scallion and 1 ½ cups of cheddar cheese. Sprinkle the rest of the cheese across the top. Cover and let the cheese melt for 10 minutes. Pile onto buns and serve!