Oh my god. These are the best thing I've made in a while. After discussion about these on Twitter early last week, I knew I had to make them for myself. And I'm so glad I did.
I made homemade caramel sauce and filled the chocolate cupcakes with it and a pinch of fleur de sel. I then made homemade dark chocolate ganache and iced the cupcakes with that and topped it with another pinch of fleur de sel. These are contenders for the best cupcakes I've ever made.