Over medium-high heat, add the milk mixture to the saucepan of garlic and stir continuously with a wire whisk until the mixture begins to thicken and bubble.
Remove sauce pan from the heat. Use a rotary cheese grater (affiliate link) to quickly shred the parmesan. Mix in the Parmesan, stirring until it melts completely.
Serve immediately, or store in an airtight container in the refrigerator for up to 5 days.
Notes
This recipe makes approximately 3 cups of alfredo sauce. For the milk, use your variety of choice. I use 2% milk, but skim still tastes good as well.