Using an electric mixer, whisk together the margarine, butter and sugar together until pale and creamy. Add the eggs one at a time. Add the vanilla essence.
Sift together the flour and baking powder and slowly add to the creamed mixture with the 180 ml (¾ C) milk.
Divide the batter into two bowls. To one bowl add the cocoa powder and the 15 ml (1 T) milk.
Drop large spoons of each mixture into a cake pan that has been sprayed with non-stick spray. Use the back of a fork to run through the cake mixture so that you create a marble effect of the brown and white batters.
Bake in an oven that has been preheated to 180°C for 50 minutes or until a skewer inserted in the middle of the cake comes out clean. Allow to cool.
To make the white ganache, break the white chocolate into a bowl. Heat 80 g of the cream and then pour the cream over the chocolate. Stand for two minutes and then whisk to smooth. Allow to cool, stirring every few minutes until the ganache thickens.
Repeat using the dark chocolate and remaining 80 g of cream.
Pour the dark chocolate ganache over the cake and allow to run a little down the sides. Leave to set. Pour the white chocolate ganache over the dark chocolate ganache. Leave to set.
Decorate with white chocolate curls.Recipe reprinted with permission of Pomegranate Days. To see more recipes, click here.