1. Place the sugar in a pan over a average heat. Brush the sides of the pan with a pastry brush dipped in a mug of chilly water. Carry on this process until the sugar caramelizes. (You will probably end up using a third of the water).
2. Add the rest of the water, coffee beans, cocoa powder, salt and chocolate.
3. Bring to the boil.
4. Pass through a very fine sieve and allow cooling.
5. Serve cold.