Bring the cream and milk to a simmer in a heavy-bottomed pan.
Add the sugar and stir to dissolve into the simmering liquid.
Split the vanilla pod in half with a sharp knife and scrape out the seeds. Add the vanilla pod and seeds to the milk and cream mixture, then remove from the heat. Leave to cool and to infuse the vanilla flavours, for at least five minutes.
Meanwhile, soak the gelatine leaves in a bowl of cold water until softened and pliable, about 3-4 minutes. Squeeze the extra water from the gelatine, then add the leaves to the hot cream/milk mixture. Stir until dissolved.
Add the coffee granules to the milk and cream and stir until the granules are completely dissolved. Strain the cream mixture through a sieve into a jug. Discard the vanilla pods. Leave to cool for a few minutes.
Pour the mixture into dariole moulds. Place in the fridge and leave to set for three hours.
A few minutes before you're ready to serve, make the chocolate sauce. Place half of the water in a pan and bring to the boil.
Add a small amount of chocolate pieces to the boiling water and stir until the chocolate melts. Add more water and chocolate bit by bit, until the sauce reaches the desired consistency. Whisk constantly over a low heat.
When the panna cottas have set, remove them from their moulds by dipping the bases of the moulds into a bowl of very hot water to loosen them. You may laso need to run a knife around the edge of each panna cotta.
To serve, turn each of the panna cottas out of the moulds onto a plate. Drizzle with chocolate sauce and place some amaretti biscuits alongside.
