Mix the espresso, caster sugar and amaretto, to taste, in a large bowl.
Add the panettone slices to the coffee mixture and set aside.
Place the mascarpone, vanilla seeds and icing sugar into a separate bowl and mix together.
Add the double cream and fold into the mascarpone mixture.
Place a piece of soaked panettone onto each plate. Add a spoonful of the mascarpone and cream mixture to each soaked panettone slice, then place another panettone slice on top to make a sandwich.
Spoon more cream over the top and sprinkle with the cocoa powder and a little coffee powder. Transfer to the fridge to chill for 1-2 hours.
To serve, remove from the fridge and sprinkle with gratings of dark chocolate.