Beat 250g softened, unsalted butter for 2 minutes. Sieve in 500g icing sugar and pulse briefly. Add 1 teaspoon vanilla extract and beat on full speed until very light and fluffy.
Orange: add the grated zest of 2 oranges and 4 tablespoon of juice.
Lemon Curd: stir 275g of lemon curd in to 750g of buttercream. (Try orange curd too). This is a good alternative to fresh cream for filling a vanilla cake which is to be covered in chocolate or marzipan/icing.
Expresso: pour 2ooml freshly boiled water on to 100g of fresh ground coffee and allow to steep for 5 mins. Strain and leave to cool slightly. Stir into a quantity of buttercream to taste.
Chocolate ganache: heat 125g fresh double cream to the boil and pour over 175g dark chocolate, broken into pieces. Stir with a wooden spoon until chocolate is melted to a glossy puddle. Allow to cool for 15 minutes before beating into 750g buttercream. Will keep for 2 weeks in the fridge.