Heres why the combination worked: When chocolate melts, the cocoa butter becomes liquid. All its other components are insoluble and are suspended in the liquid. Because white chocolate contains cocoa butter but no cocoa solids, it created a more fluid product that was easier to work with and allowed for a thinner coating. Also, the more cocoa butter there is, the more rigid (snappy) and glossy the final coating will be. Avoid white chocolate chips and any bars that contain partially hydrogenated palm oil, palm kernel oil, soybean oil, or cottonseed oil, as these are added in lieu of some or all of the cocoa butter and thus wont work as well.

Heres our cheater method: Finely chop or grate 4 ounces of chocolate and 1/4 ounce of white chocolate. Microwave 3 ounces of the dark chocolate at 50 percent power until it is mostly melted, stirring frequently. Then add the remaining 1 ounce of chocolate and the white chocolate and stir it until melted, returning it to the microwave for no more than 5 seconds at a time to complete the melting.