Do I use unsweetened, sweetened or bittersweet chocolate for this recipe?

The recipe suggests using a chocolate of 70%, which is usually bittersweet. If you used an unsweetened version, you might need to adjust the sugar content to have it be sweet enough. Lower percentage chocolate, even milk chocolate, would work- but the chocolate flavor won't be as intense because there will be less of the chocolate solids to flavor it. I made it with an 85% bittersweet, added a bit more sugar, and it was to die for. My daughter made it once with semi-sweet chips, and it was not as intense- but hey, chocolate cake is good anyway you look at it.

The recipe writer specifies that she used 70% chocolate so I would use bittersweet chocolate.