Put the sugar and water into a heavy-based pan. Heat gently until all the sugar has dissolved. Then increase the heat slightly and gently boil for 5 - 6 minutes until golden brown - do not be tempted to stir during this process as the sugar will crystallise.
Once the caramel starts to colour, swirl the pan gently to ensure it does so evenly, but don't stir. The deeper the colour, the better the flavour - just don't burn it.Remove from the heat, and carefully stir in the cream and butter until well incorporated.
If you are making salted caramel then add the sea salt together with the cream and butter.
Leave to cool slightly and then transfer to a sterilised jar and keep refrigerated.