Place the chicken breasts in a 6 quart slow cooker liner.
Pour the condensed cream of chicken soup over the chicken breasts.
Add the sour cream and use a rubber spatula to gently swirl the soup and sour cream together.
Sprinkle the diced onion and dried parsley over the top.
In a small bowl, toss together the dry stuffing mix and melted butter. Sprinkle evenly over the top.
Cover the slow cooker and cook on low for 6-7 hours or on high for 3-4 hours.
If desired, uncover the last 45 minutes of cooking so that the stuffing firms up a little. It won’t be a “crispy” stuffing topping, but can help the texture. This isn’t necessary though and tastes just as good without.
Season with salt and pepper and serve with mashed potatoes and a vegetable.
Store leftovers in an airtight container in the fridge for up to 3 days.