Combine the avocados, parmesan, and garlic in blender or food processor and blend until mostly mashed.
Add the milk and blend/puree until smooth and creamy. Season with salt & pepper to taste and enjoy!
Combine the sauce with your noodles or zoodles JUST BEFORE serving. It will last a couple of hours mixed, but not long. I recommend combining only enough for that specific meal.
Notes
To store this sauce without browning, smooth it down into a container and cover it with a thin layer of lemon or lime juice. I tried using plastic wrap, as well as the water method, and neither worked. Only the thin layer of lime juice worked. You can choose to pour it off, or just stir it in! Another option is to place this in a storage container with a very small opening, and then just scoop off or mix in the top brown part when serving.