In a small bowl, mix together all the ingredients except the buttercream.
Add the butter and the milk and mix well.
Add a splash of cream, a sprinkling of sugar and the vanilla bean and mix again.
Pour the mixture into a 9cm (3in) round cake pan.
Cook for 10-12 minutes until golden brown and smooth.
Serve with buttercream icing and a sprinkle of powdered sugar for decoration.