Method:

1. Put the butter and the chopped chocolate into a bowl that sits over a pot of boiling water. The steam will gently melt the chocolate, so that you can easily mix it with the butter. 

2. In a second bowl, beat the egg and sugar until frothy. Add the cocoa along with the flour and beat until smooth. Pour in the melted butter and chocolate mixture and mix well. 

3. Transfer the mixture to a greased, six-cup muffin pan and bake for seven minutes at 220 C°.