Preheat oven to 375°F and lightly grease a 9x13 casserole dish.
Add the uncooked macaroni, diced raw chicken and broccoli straight into the dish.
Sprinkle with garlic powder, onion powder, paprika, salt and pepper.
Pour in the chicken broth and milk. Add cubes of cream cheese. Stir everything really well, making sure the macaroni is mostly submerged in the liquid.
Cover tightly with foil — this part is important because you need that steam to cook the pasta.
Bake covered for 35 minutes.
Remove from the oven and give everything a really good stir. Check the pasta. If it’s still pretty firm, cover and bake another 10 minutes.
Once the pasta is tender and the chicken has reached 165°F, stir in 1½ cups cheddar cheese.
Top with the remaining ½ cup cheddar and bake uncovered for 5–10 minutes, just until melted and bubbly.
Let it sit for about 5 minutes before serving. It’ll thicken as it rests.