Roughly chop the chocolate. Melt the butter and chocolate in a saucepan over low heat while stirring. Remove from the stove. Whisk the eggs. Coarsely chop the nuts, except for some for decoration. Put melted butter and chocolate in a large mixing bowl.
Add 500 g sugar, vanillin sugar, salt, eggs, flour and baking powder. Mix with the whisks of the hand mixer to a smooth dough. Stir in nuts. Grease the fat pan of the oven (32 x 39 cm) well. Spread the dough evenly over it. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 30 minutes. Remove from the oven and let it cool down on a cake rack. In the meantime, chop the chocolate coating coarsely for the icing. Stir cream, couverture and coconut oil in a small pot at low heat until a creamy mixture is formed. Remove from the heat, allow to cool for about 15 minutes and spread evenly on the cake. Put the cake in a cool place for 1 1/2-2 hours. Then cut into 60 pieces.
Remove from the oven and let it cool down on a cake rack. In the meantime, chop the chocolate coating coarsely for the icing. Stir cream, couverture and coconut oil in a small pot at low heat until a creamy mixture is formed. Remove from the heat, allow to cool for about 15 minutes and spread evenly on the cake. Put the cake in a cool place for 1 1/2-2 hours. Then cut into 60 pieces. To decorate, caramelise 2 tablespoons of sugar in a pan. Place the remaining nuts on baking paper and sprinkle with the caramel