Preheat the oven to 350°F (175°C).
Cook the pasta according to package instructions until al dente; drain and set aside.
In a large mixing bowl, combine cooked pasta, chicken, broccoli, cream, garlic powder, salt, and pepper. Mix well.
Fold in 1 1/2 cups of cheddar cheese and 1/4 cup of Parmesan cheese into the mixture.
Transfer the mixture to a greased baking dish, spreading it evenly.
Top with remaining cheddar, Parmesan, and breadcrumbs if desired.
Cover with foil and bake for 25 minutes. Remove foil and bake for an additional 15 minutes until golden and bubbly.
Let stand for 10 minutes before serving.