Preheat oven to 160C.
Place the chocolate and cocoa powder in a medium saucepan over low heat bainmaree, stirring until the chocolate melts and the mixture is smooth.
Add the cream slowly until amalgamated well
Add orange zest and Cointreau and mix well till smooth
Remove from heat and add the egg and whisk until combined.
Pour into the pastry case and bake in oven for 30 -35 minutes or until just set
Set aside for 3-4 hours to cool.
Add orange segments, icing sugar and mint leaves to dress