Line a 6-hole muffin tray with paper cake cases.
Cream together the butter and caster sugar using a hand-held electric whisk until light and fluffy. Beat in one egg, half the milk and the vanilla, then the plain flour. Stir in the remaining egg and milk. Add the self-raising flour, stirring until just combined. Use to fill the cake cases, reserving the excess to make a second batch. Place on the lower rack of the halogen oven.
Set the temperature to 200°C (392°F) and cook for about 15 minutes until risen and just firm to the touch. Leave in the tin for 5 minutes, then transfer to a wire rack while you cook the remaining mixture.
Make the icing. Put the cream cheese, chocolate, butter, vanilla and icing sugar in a bowl and beat until smooth and creamy. Spread over the tops of the cakes. Scatter with plenty of white chocolate curls and dust with extra icing sugar to decorate.