Roughly chop 300 g chocolate. Melt butter and chocolate in a small pot at low heat. Remove from the stove. Whisk the eggs. Roughly chop the nuts.
Put melted chocolate into a large mixing bowl. Add sugar, vanilla sugar, salt, eggs, nuts, flour and baking powder. Mix with the whisk of the hand mixer to a smooth dough. Pour the dough evenly onto the well greased fat pan of the oven and bake in the preheated oven (electric oven: 175 °C/ gas: level 2) for approx. 30 minutes. Remove from the oven and let it cool down on a grid. In the meantime, break the remaining chocolate into pieces for the icing. Melt cream, chocolate and coconut oil in a small pot at low heat while stirring. Let it cool down for about 15 minutes and then spread it on the cake. Chill the cake for 1 1/2 -2 hours. Cut into 60 pieces.
In the meantime, break the remaining chocolate into pieces for the icing. Melt cream, chocolate and coconut oil in a small pot at low heat while stirring. Let it cool down for about 15 minutes and then spread it on the cake. Chill the cake for 1 1/2 -2 hours. Cut into 60 pieces. Decorate as you like with chopped pistachios. Serve with vanilla ice cream and chocolate sauce