Preheat oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.
Spread diced chicken evenly in the baking dish. Season lightly with salt and pepper.
Layer ham evenly over the chicken, then sprinkle with shredded cheese.
In a bowl, whisk together cream, chicken broth, Dijon mustard, garlic powder, and onion powder.
Pour sauce evenly over the casserole.
If using topping, mix breadcrumbs with melted butter and sprinkle over the top.
Bake uncovered for 35–40 minutes, until bubbly and chicken is fully cooked.
Let rest 5–10 minutes before serving.