Mix together the cream of chicken soup and milk in a small bowl. Pour enough of the soup into a slow cooker to cover the bottom.
Layer chicken breasts over the sauce. Cover with slices of ham and then Swiss cheese.
Pour the remaining soup over the layers, stirring a little to distribute between layers.
Sprinkle the stuffing on top, and drizzle butter over stuffing.
Cover and cook on low for 4 hours, or high for 2-3 hours.
Notes
This dish tastes the best when you can cook it on low for about 4 hours. Any more than that and the chicken will dry out.
I don't recommend leaving this in your slow cooker on warm for too long after the 4 hours are finished, just because the chicken will start to dry out. I would recommend serving it pretty quickly after it finishes cooking.