Place the sugar in a pan over a medium heat. Brush the sides of the pan with a pastry brush dipped in a mug of cold water. Continue this process until the sugar caramelises. (You will probably end up using a third of the water).
Add the rest of the water, coffee beans, cocoa powder, salt and chocolate.
Bring to the boil.
Pass through a very fine sieve and allow to cool.
Serve cold.