Place cocoa butter in a microwave safe bowl and heat on high for one minute. Then heat on high at 30 second increments until it is fully melted. This will take longer than with other fats and oils, because cocoa butter is fully solid at room temperature.
Stir in powdered erythritol and powdered milk until dissolved.
Stir in vanilla extract and salt.
Spoon mixture into whatever candy mold floats your boat. Place molds inside refrigerator until white chocolate is solid, about an hour.
To remove from candy molds, simply turn upside down and press on top of each mold to release.