Technically, white chocolate is not chocolate at all as it has not cocoa solids in it, but a lot of people have been asking for a recipe, so here it is.

Ingredients

16 oz Cocoa butter
1 t lecithin
14 oz powdered dry milk (yes, this is what the professionals use)
14 oz sugar
You can also consider adding a few once of milk fat (clarified butter) as in done by most professionals or even Cream powder. It makes a slightly different white chocolate.

Procedure:

Because there are no cocoa solids present, you don't have to worry about roasting, cracking or grinding any cocoa beans. You can go straight to the Santha for refining.

Place the melted Cocoa butter in your Santha Wet Grinder. It is very helpful to have your solid ingredients warmed up to at least 120 F, including the Santha drum. Slowly add the 14 oz of sugar and 14 oz of milk powder into the melted cocoa butter while the melanger is running. Run the Melanger until the white chocolate is of the smoothness you desire. I find 8-10 hours is about right. Your tastes may vary.
After it is out of the Melanger temper and mold up your chocolate into the shape of your choice.
Place into a cool, dry place to solidify and then unmold, usually about 24 hours later to be safe. This can be done in a refrigerator if you wish.
I have not found that white chocolate benefits from the resting like real chocolate, but I have found you need to protect it from heat and light a bit more or it can turn "off".

Enjoy!