Spray an 11x7x2-inch (2½-quart) baking dish with cooking spray.
If you are going to make the homemade alfredo sauce, do that now and set it aside (my alfredo sauce recipe, as written, will make the 2 cups you need for this recipe).If you will be using jarred sauce, move on to the next step.
Cook the ziti in boiling salted water according to the package directions for one minute less than al dente (this will help ensure that the pasta doesn't overcook and become mushy while in the oven); drain.While the ziti is boiling, move on to cooking the chicken.
Heat the olive oil in a large skillet over medium heat. Add the chicken, season with the garlic powder, salt and pepper (I use ½ teaspoon salt and ¼ teaspoon pepper); sauté, stirring frequently, just until the chicken is cooked through and no longer pink.
In a large bowl, combine the cooked ziti, cooked chicken, thawed broccoli florets, and alfredo sauce; stir until everything is evenly coated with sauce.
Transfer the ziti mixture to the prepared baking dish.
Sprinkle the mozzarella cheese evenly over the ziti mixture.
Bake, uncovered, for 25 to 30 minutes or until the sauce is bubbly and the cheese is melted and starting to get lightly golden.
Let the casserole rest for 15 to 20 minutes before serving (this will give the sauce a chance to thicken up a bit; it will be a little loose right out of the oven). Enjoy!
Recipe Notes
If making homemade alfredo sauce, you will need to add about 15 minutes to the total time.
If using jarred alfredo sauce, one 15-ounce jar will give you about 1¾ cups, which is fine to use for this dish (this is the size jar I see the most in the grocery store). If you can find a slightly larger jar, that would be even better.
Don't cook the frozen broccoli, just thaw it before using. Because frozen broccoli is already partially cooked and it will cook more in the oven, you don't want it to end up mushy.
To keep the calories somewhat in check, this isn't swimming in alfredo sauce. There's just enough to add lots of great flavor and make it creamy. If you'd like extra sauce, go ahead and use more.
Because of the richness of this dish, I like to do 6 smaller servings. If you don't mind the extra calories, you could always divide it into 4 very generous servings.
Please refer to the post for additional recipe tips, substitutions and variations, serving suggestions, and information on making ahead, storing, freezing, and reheating.
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