While with Marco Pierre White at The Restaurant we used to make a small version of this for a tray of chocolates served with coffee – it was very classy.
Put the raisins in an airtight container and add the rum. Seal and and leave to marinate overnight.
Put the cream and invert sugar into a saucepan, bring to the boil and then leave to cool to 65-70°C (149-158°F). Melt the chocolate over a bain-marie (water bath) to about 45°C (113°F), then gradually add the cream to the chocolate, mixing continuously to form an