- Preheat the oven to 375°F. 
- Boil pasta in salted water according to package directions. Reserve 1 cup of pasta water and drain the rest. Set the noodles and reserved pasta water aside. 
- In a large oven-safe skillet over medium heat, melt the butter. Add the minced garlic and cook for 30 seconds. 
- Add the all-purpose flour to the skillet and whisk it together with the butter, cooking for 1 more minute. 
- Slowly drizzle in the milk and heavy cream, whisking constantly until the mixture thickens enough to coat the back of a spoon. 
- Add the parmesan cheese, ½ cup of shredded mozzarella cheese, onion powder, kosher salt, and black pepper. Continue to stir until the cheese is completely melted and the sauce is smooth. 
- Add the rotisserie chicken and cooked pasta. Stir to combine everything evenly with the sauce. If your sauce is too thick, add some reserved pasta water, stirring to combine. 
- Sprinkle the remaining shredded mozzarella cheese over the top of the dish. 
- Bake, uncovered, for approximately 20 minutes or until cooked through and lightly browned. 
- Garnish with finely chopped fresh parsley and serve.