1 lb. Unsalted Butter
1 lb. Caster Sugar
4 oz. Brandy

Soften the butter a little (dont let it melt).
Put the butter and caster sugar in a food processor and whizz until it is white and fluffy.
While it is beating add the Brandy – a tablespoon at a time – through the top of the processor.
Make sure the last spoonful is amalgamated before adding another.
Let this set in the fridge – it will keep there for weeks – but leave it out at room temperature for several hours before using.