Divide 400 g chocolate into pieces. Melt with butter in a hot water bath. Leave to cool a little. Wash, clean and grate the zucchini. Chop the walnut kernels. Mix flour and baking powder.
Whisk the eggs in a large mixing bowl. Add liquid chocolate, sugar, vanilla sugar, 1 pinch of salt, 10 eggs and flour mixture. Stir everything briefly with the whisks of the mixer to a smooth dough. Fold in zucchini and nuts.
Place the dough in a greased, flour-blasted fat pan (approx. 32 x 39 cm). Bake in a preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for 25-30 minutes. Let them cool down.
Heat the cream and coconut oil. Cut 250 g chocolate into pieces and melt in the hot cream. Let cool for about 5 minutes. Stir with a whisk until smooth and pour immediately onto the cooled cake. Smooth and let dry.
Sieve the icing sugar into a bowl. Add 1 egg white and mix everything with the whisk of the mixer to a smooth icing. Pour into the freezer bag and cut off a small corner. Labele the cake with icing and decorate with chocolate lentils.