Preheat your oven to 350°F (175°C), ensuring it reaches the correct temperature for even cooking.
Prepare the chicken: Lay the chicken breasts flat in the baking dish, creating an even layer.
Mix the soup and milk: In a bowl, combine the cream of chicken soup with milk, stirring until smooth.
Layer the casserole: Pour the soup mixture over the chicken, spreading it evenly. Sprinkle the shredded Swiss cheese on top, followed by the herb-seasoned stuffing mix. Drizzle the melted butter over the stuffing.
Bake: Cover the dish with foil and bake for 50 minutes. Remove the foil and bake for an additional 10 minutes or until the topping is golden brown and the chicken is thoroughly cooked.