250g (9 oz) butter or Vitalite (for dairy free)
500g (18 oz) icing sugar
1 teaspoon vanilla extract
1 tablespoon milk (almond or soy milk for dairy free)
Paste food colouring if you want to colour it
Make sure the butter is at room temperature and soft. If you take it straight from the fridge then you'll need to microwave it for a few seconds.
Beat the butter in a large bowl until soft. Add half of the icing sugar and beat until smooth.
Add the remaining icing sugar and the milk and beat the mixture until creamy and smooth. Note: this will take at least six minutes in an electric mixer, and probably about twelve minutes by hand.
Stir in the food colouring if used, and mix well until thoroughly combined.
Store in a sealed container in the fridge for two days maximum.
p.s. if you use soft spread marg, then leave out the milk.