Cook the noodles according to the package instructions to al dente with 1 teaspoon of salt, drain and keep in a pot with room temp water. This will help the noodles not stick together.
Preheat the oven to 375°F/190°C, and a spray a 9x13 inch pan with cooking spray and set aside.
Over medium heat, melt butter in a pan, then sauté the garlic until fragrant (about 1 minute). Add the flour, and cook it for 1 minute. Add the milk, and heavy cream. Allow the mixture to simmer for 2 minutes, then add the parmesan cheese, salt, pepper, and nutmeg if using. Whisk and cook until the cheese is melted and the sauce is thickened. If the sauce thickens too much, add a little bit of milk to loosen it but this is unlikely to happen.
Spoon a thin layer of sauce onto the bottom of the baking dish (about ½ a cup).
In a bowl, mix together 1 cup of alfredo sauce with the shredded chicken and 1 cup of mozzarella cheese. Season with salt and pepper.