2. Pour 100g of the caster sugar into a large frying pan and place it over a medium heat, shaking the pan occasionally, but not stirring, to ensure it melts evenly. Once it has turned a deep golden colour, scatter it with the mint leaves and tip on to the prepared tray. Set aside to cool. When cold and firm, break half the caramel into pieces and place in a bowl. Using the end of a rolling pin, crush them into very small pieces and set aside. Break the remaining caramel into small shards and reserve for decoration.