Preheat your oven to 350°F (175°C).
Cook the pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, melt the butter over medium heat. Add the diced chicken and season with salt, pepper, and garlic powder. Cook until the chicken is no longer pink, about 5-7 minutes.
Add the broccoli florets to the skillet and cook for an additional 3-4 minutes until they are tender.
In a large mixing bowl, combine the cooked pasta, chicken, broccoli, heavy cream, and shredded cheddar cheese. Mix well until everything is combined.
Transfer the mixture to a greased baking dish, spreading it evenly. Sprinkle the grated Parmesan cheese over the top.
Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden.
Remove from the oven and let cool for a few minutes before serving.