Heat the oven to 400°F and grease a baking dish.
Season chicken pieces with salt, pepper, and garlic powder.
Spread chicken in an even layer in the dish.
Add diced ham evenly over the chicken.
Sprinkle shredded Swiss cheese on top.
Combine heavy cream, cream cheese, chicken broth, Dijon mustard, garlic powder, and salt in a saucepan.
Heat and stir until smooth.
Pour the sauce evenly over the casserole.
Bake 25–30 minutes until bubbling and lightly browned.
Let rest 5 minutes before slicing.