Bring the cream, sugar, vanilla sugar, vanilla bean seeds to a boil. Remove from heat and stir in the chopped chocolate. Let cool then chill for about 2 hours in the refrigerator.
Whip the chocolate mixture until fluffy then beat in the softened butter. Transfer to a piping bag with a large star tip and pipe rosettes onto a sheet of parchment paper. Chill for 1 hour.
Whisk the egg white and orange zest. Roll the truffles in egg white mixture then powdered sugar and let dry. Serve in the foil cups.