Melt the chocolate in a heatproof bowl set over a pan of gently simmering water, making sure the bottom of the bowl is not in contact with the water. Remove from the heat and leave to cool slightly.
Beat the butter in a large bowl until light and fluffy. Add a tablespoon of icing sugar and beat well to combine. Now beat in a tablespoon of brandy also until well blended. Continue in this way, beating the icing sugar and brandy alternatively into the mixture until both are used up.
Add the slightly cooled chocolate and mix well. Make sure the chocolate is not too hot or it will melt the butter. If uncertain, add a tablespoon first and if it starts to melt the butter, wait until it is a little cooler before adding the rest.
Place in a sealed container and store in the fridge. It will keep well for 2-3 weeks. Remove from the fridge 1-2 hours before serving to allow to soften