Covers a 20cm round cake. Make a smaller batch just for filling.
- 150g unsalted butter, softened at room temperature
- 0.5tsp vanilla extract
- 375g icing sugar
- 75g white/milk chocolate
- Break the chocolate into pieces and melt in a bowl over a saucepan of water.
- Cream the butter, vanilla and sugar together.
- Mix in the melted chocolate and leave to cool.