Boil the butter, cocoa, oil and water together on the stove.
In a separate bowl mix together the flour, sugar and salt.
Add the cocoa mixture to the flour mixture and stir.
In a smaller bowl, mix together the bicarb and the yoghurt--watch it bubble!
Add the eggs one at a time to the yoghurt mixture and beat it all together.
Add the yoghurt mixture to the chocolaty mixture and stir it all together.
Bake at 180°C (about 350°F for about 30 minutes.
Break chocolate into pieces and place these onto the cake as soon as it comes out of the oven. wait a bit, for the cake to cool and the chocolate to melt then spread the chocolate over the cake AND ENJOY!