Place the chicken breasts in the bottom of the Crock Pot. Season with salt and pepper.
In a mixing bowl, combine the cream of chicken soup, softened cream cheese, and ranch dressing mix. Stir until well blended.
Pour the cream mixture over the chicken in the Crock Pot. If using, add the sliced mushrooms on top.
Cover and cook on low for 6 to 8 hours or on high for 3 to 4 hours, until the chicken is cooked through and tender.
About 30 minutes before serving, sprinkle the shredded cheddar cheese over the chicken and cover again to allow the cheese to melt.
Once done, shred the chicken with two forks and stir to combine with the sauce. Garnish with chopped parsley before serving.