Make the Orange Creme Fraiche: Combine all the ingredients in a chilled bowl and whisk until soft peaks form. Chill until ready to serve.
Make the Pudding: In a bowl whisk together the sugar and cornstarch to blend. Whisk in the cream, milk, and vanilla bean. Pour mixture into a stainless steel saucepan and bring it to a boil, whisking, until thickened, about 4 minutes.
Remove the pan from the heat and whisk in the chocolate and butter until melted. Fish out the vanilla bean and rinse it. Wrap the vanilla bean in plastic wrap and refrigerate for another use.
Pour the hot chocolate into warmed demitasse cups and serve immediately with dollops of the orange creme fraiche served on the side on demitasse spoons.