To brown the chicken (optional): if your crockpot has a saute setting, spray the inside with cooking spray and set to saute. If your crockpot doesn't have a saute setting, spray a skillet with cooking spray and heat over medium-high heat.
Blot the chicken dry with a paper towel and add to the crockpot or skillet. Cook for 3 - 5 minutes or until the chicken is lightly browned. Turn and repeat on the other side.
If using a skillet to brown the chicken, transfer the chicken breasts to the crockpot after browning.
Add the chicken stock, cream cheese, ranch dressing mix, and pepper. Cover and cook on low heat for 4 hours or until the chicken is cooked through and reaches an internal temperature of 165 F (74 C).
When the chicken is cooked, remove the chicken from the crockpot and whisk the sauce until it is smooth. For a thicker sauce, return the crockpot to the saute setting (high if possible) and cook, whisking frequently for 5 to 10 minutes.
If your crockpot doesn't have a saute setting, pour the sauce into a saucepan and heat over medium-high heat, whisking frequently until the sauce thickens to the desired consistency.
Garnish with the bacon and sliced green onions before serving if desired.