Why is my chocolate ice cream grainy?

I know some of you feel that chocolate ice cream isn't really chocolate ice cream unless there is A LOT of chocolate in it. And here is where the problem of grainy chocolate ice cream might happen.

In the process of mixing an excessive amount of cooking chocolate into the ice cream custard base, you (a) did not melt down the cooking chocolate beforehand and/or (b) left the ice cream custard to freeze before you allowed the cooking chocolate to be completely mixed and dissolved.

So, the bottom line is, always make sure you mix the cooking chocolate into the custard until it is smooth and shiny. Microwave the cooking chocolate for 10 to 15 seconds if you must to soften it before using. Anything other than a smooth and shiny melted chocolate mix would give you a lumpy texture that is less palatable.