Prepare chocolate cake according to package instructions. Over bake the cake for about 5-8 minutes. Let it cool completely.
In a glass measuring cup or mixing bowl, pour in heavy whipping cream. Microwave for 30 seconds to 1 minute until cream is very hot but not boiling.
Add in chopped chocolate. Mix slowly to avoid too many air bubbles. Mix until chocolate has melted into the cream and, then add in the butter.
Yield: 8-10 servings