Gently heat milk in saucepan, just until barely simmering. Remove and keep covered.

Melt butter. When foam subsides, add flour and stir until smooth. Cook 1-2 minutes, stirring. Do not allow flour to color.

Gradually add the warm milk, whisking to combine.

Add the salt and cayanne and increase the heat to medium.

Cook the mixture, whisking continuously, until the sauce comes to a boil and is thickened.

Remove from heat and add the garlic.

Pour the hot mixture into a blender, cover tightly, and process until smooth.