Heat the double cream gently with the vanilla pod until boiling. Remove from the heat, remove the vanilla pod and add the chocolate. Stir until melted.
Whisk together the egg yolks, golden caster sugar and vanilla sugar with the brandy, until the mixture becomes thick, foamy and pale. Gradually pour on the chocolate cream and whisk in, then strain back into the cleaned pan. Gently heat the mixture, stirring continuously until it has become thick and smooth.
Fill 6 heatproof glass espresso cups with the chocolate custard, then chill for at least 2 hours. Spoon a dollop of clotted cream on to each cup. Sprinkle the top of each cup with dark muscovado sugar, then use a chef's blowtorch or hot grill to caramelize the sugar.