Have a sheet of greaseproof paper ready on a heatproof surface. Measure the 2 tbsps water into a heavy bottomed pan. Cover with the sugar and place over a medium heat until the sugar starts to dissolve. Do not stir.
Once the sugar starts to dissolve increase the heat to medium high until the sugar is a dark golden brown.
Pour the caramel on to the greaseproof paper in a thin and even layer. Leave to cool, then use a sharp knife to carefully chop into smallish shards.
Use immediately or store in a plastic bag or sealed container in the freezer.