Savory Baked Garlic Parmesan Chicken Pasta with Mozzarella

Ingredients

• 1 lb (450 g) rotini pasta
• 3 cups (420 g) cooked chicken, shredded or diced
• 1 cup (240 ml) reserved pasta water, divided
• 2 jars, 15 oz each (425 g each), Alfredo sauce
• 1 cup (240 ml) garlic Parmesan sauce
• 1/2 teaspoon kosher salt, plus more for pasta water
• 1/4 teaspoon black pepper
• 1/4 teaspoon red pepper flakes, optional
• 2 cups (225 g) shredded mozzarella cheese, divided
• 1/2 cup (50 g) grated Parmesan cheese, divided
• 1 tablespoon butter or cooking spray, for greasing the dish
• 2 tablespoons chopped fresh parsley, for serving