For the cake:
250g unsalted butter, softened
150g white chocolate, chopped coarsely
1 1/4 cups caster sugar
1 cup milk
1 1/2 cups plain flour
1/2 cup self raising flour
1 tsp vanilla extract
2 eggs, beaten lightly
For the white chocolate ganache:
1/2 cup cream
300g white chocolate, chopped coarsely
Preheat oven to 175 degrees C. Grease a 20 cm round cake pan and line the base with baking paper.
Place butter, 150g white chocolate, sugar and milk in a saucepan. Stir over low heat until the chocolate melts. Transfer the mixture to a large bowl then let cool for around 15 minutes.
Stir in the flour, eggs and vanilla extract. Pour the batter into the prepared pan.
Cover the pan loosely with aluminium foil (to prevent excess browning on the top of the cake) and bake the cake for 1 hour.
Remove the foil and transfer the cake to a wire rack to cool.
To make white chocolate ganache: combine cream and 300g white chocolate in a saucepan over low heat, stirring constantly until the chocolate melts. Transfer to a bowl and cool until the ganache is spreadable.
Place cake on a serving plate then cover the top and sides with white chocolate ganache.