Preheat the oven to 350ºF. Grease an 8 inch cake pan (the smaller the pan the higher cake and vice versa).
In a medium bowl stir together oil, milk, sugar, eggs and yogurt. Add cocoa, flour and baking powder into the bowl and stir until the mixture is well blended. Stir in the chopped chocolate.
Pour the mixture into the cake pan and put into the oven for about 35 minutes or until a toothpick poked into the center of the cake comes out clean.
While the cake is in the oven prepare the icing: Put the heavy cream in a small sauce pan and bring to boil. Stir in the chocolate until is completely melted. Remove from the heat and let it cool.
Let the cake cool then gently remove it from the pan onto a plate or a cake stand.
Pour the chocolate icing on top of the cake and with a knife or offset spatula, spread it evenly over it (Feel free to let the icing spill sideways or to keep it on the top as is in my cake). Gently place your flower in the middle of the cake and serve.