Preheat oven to moderate 180oC.
Brush a deep, 20cm round cake tin
with melted butter or oil. Line base and side with paper, grease
paper.
Using electric beaters, beat butter
and sugar in small mixing bowl until light and creamy. Add eggs
gradually, beating thoroughly after each addition. Add essence, beat
until combined.
Place chocolate in glass bowl. Stir
over barely simmering water until melted, remove from heat.
Transfer butter mixture to large
mixing bowl, add chocolate and yoghurt.
Using a metal spoon, fold in sifted
flour. Stir until just combined and the mixture is almost smooth.
Pour mixture into prepared tin, smooth
the surface.
Bake for 40 minutes or until skewer comes out clean when
inserted in centre of cake.
Stand cake in the tin 15 minutes before
turning onto wire rack to cool.
To make the White Chocolate Topping
: Using electric beaters, beat cream cheese in small mixing bowl
until light and creamy. Add chocolate and yoghurt, beating 5 minutes or
until mixture is smooth and fluffy.
Spread icing completely over cake
using a flat-bladed knife. Decorate cake with white chocolate curls.