Roughly chop the chocolate. Melt butter and chocolate in a small pot at low heat while stirring. Remove from the stove. Whisk the eggs. Coarsely chop the nuts.
Put the melted chocolate into a large mixing bowl. Add sugar, vanillin sugar, salt, eggs, nuts, flour and baking powder. Mix with the whisks of the hand mixer to a smooth dough. Pour the dough evenly onto a well greased fat pan. Bake in a preheated oven (electric: 175 °C/ gas: level 2) for approx. 30 minutes. Remove from the oven and leave to cool on a grid. In the meantime, roughly chop the chocolate coating for the icing. Melt the cream, couverture and coconut oil in a small pot at low heat while stirring constantly. Remove from the heat, let it cool down for about 15 minutes and then spread evenly on the cake. Refrigerate the cake for 1 1/2-2 hours.
Remove from the oven and leave to cool on a grid. In the meantime, roughly chop the chocolate coating for the icing. Melt the cream, couverture and coconut oil in a small pot at low heat while stirring constantly. Remove from the heat, let it cool down for about 15 minutes and then spread evenly on the cake. Refrigerate the cake for 1 1/2-2 hours. Then cut into 60 pieces. Serve decorated as desired with cream tuff and walnuts