1. Boil water in a large pot and cook ziti pasta until al dente, then drain.
2. In the last few minutes of boiling, add broccoli florets to the same pot to cook, then drain with pasta.
3. In a saucepan, melt butter over medium heat and sauté minced garlic until fragrant.
4. Sprinkle flour over the butter and stir to create a roux, cooking for about one minute.
5. Gradually whisk in milk (or heavy cream) and continue stirring until the sauce thickens.
6. Stir in grated Parmesan cheese and mix until smooth, then remove from heat.
7. In a large mixing bowl, combine the cooked pasta, broccoli, and prepared Alfredo sauce.
8. If using chicken, add cooked and chopped chicken pieces to the mixture.
9. Season with salt, pepper, and any additional desired seasonings like Italian seasoning.
10. Transfer the mixture to a greased baking dish and spread it evenly.
11. Sprinkle shredded mozzarella cheese generously over the top.
12. Place the dish in a preheated oven at 375°F (190°C) and bake for 15-20 minutes or until bubbly and golden.
13. Remove from the oven and let sit for a few minutes before serving.
14. Serve with garlic bread or a fresh side salad for a complete meal.
15. Store leftovers in an airtight container in the refrigerator for up to 3 days.