Grind the sugar and the milk powder separately in a coffee grinder as finely as possible.
Pour the cocoa butter in the mélangeur and then add 20 percent of the sugar. Turn on the mélangeur. Add 20 percent of the milk powder. Alternate additions of sugar with the milk powder (20 percent each time) until they are all in the mélangeur.
Let it refine for 12 to 18 hours, adding the lecithin 2 hours before the refining time is over.