Granulated Lecithin

The addition of soy lecithin acts as an emulsifier and viscosity adjuster. You will probably see it on most chocolate labels. It is purely an optional ingredient. The industry uses it for consistancy batch to batch. If you do want to use it, approximately 0.2% of any addition cocoa butter you add is about right. For an interesting effect you can add more as it will also affect the mouthfeel of your finished chocolate. A little bit will go a long way.