Place the cauliflower, milk, cream cheese, flour and salt into a blender or food processor and blend until smooth. In a large sauce pan, melt the butter over medium-high heat and add in the garlic. Sauté for a few seconds, careful not to burn.
Add the cauliflower mixture to the pan and cook, stirring constantly for 3-4 minutes or until be begins to come to a simmer. Continue to stir, cooking for a few more minutes to allow the sauce to thicken.
Once thickened, remove the pan from the heat and add in the cheese. Stir and cover immediately. Let the sauce stand for 10 minutes before using. The sauce will continue to thicken while it sits.