Combine Chelsea Caster Sugar and water in a small saucepan over a medium heat. Cook, stirring, until sugar is dissolved and mixture comes
to the boil. Do not stir once it comes to the boil, or you risk stirring in a stray sugar crystal which will ‘seed’ and cause the sugar to recrystallise. Continue cooking for 8-10 minutes or until mixture turns a rich caramel colour. Add cream and shake the pan. Stir until combined then remove from the heat and let bubbles subside. Add the milk chocolate, vanilla and half the salt, stirring until the chocolate has melted. Transfer to a medium bowl, cover and refrigerate for 30 minutes or until firm.
Line an oven tray with baking paper. Roll about 2 teaspoons of the truffle mixture into a small ball. Repeat with remaining mixture. As the mixture is quite soft you will need to give your hands a clean a few times throughout the process. Put truffles on prepared tray and refrigerate for 30 minutes or until firm.
Put the dark chocolate in a heatproof bowl over a saucepan of simmering water. Stir occasionally until it melts and is smooth. Dip each ball into chocolate to coat. Return to prepared tray. Sprinkle tops of truffles with remaining salt. Set aside for 15 minutes or until chocolate has set. Serve or package as gifts. Line a gift box with tissue paper and pop your truffles in – add a ribbon for an instant gift!