Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
In a medium bowl, whisk together cream cheese, sour cream, Dijon mustard, garlic powder, salt, and pepper.
Spread chicken evenly in the bottom of the dish. Layer ham on top, followed by the Swiss cheese.
Pour the sauce evenly over the layers.
In a small bowl, mix breadcrumbs and melted butter. Sprinkle over the top.
Bake uncovered for 25–30 minutes, until bubbly and golden.
Let cool slightly before serving. Garnish with parsley if desired.