Chop 500 g of dark chocolate coating for the base. Melt in a hot water bath. Let cool for about 5 minutes. Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Line a fat pan (approx. 39 x 32 cm; deep baking tray) with baking paper.
Stir the oil into the liquid couverture with the whisks of the mixer. Add 4 tablespoons milk, cocoa, sugar, vanilla sugar and 1 pinch of salt. Stir everything until creamy for about 2 minutes. Stir in the eggs one after the other.
Stir in the flour briefly. Spread the dough evenly on the baking tray. Bake in a hot oven for 25-30 minutes. Remove from the oven and let it cool down on the tray.
For the light chocolate cream, chop white couverture. Heat 160 ml milk in a small pot. Melt the white couverture in it, let it cool down for about 5 minutes. In the meantime, whisk 250 g butter and 450 g icing sugar with the whisk of the mixer for about 5 minutes until light creamy.
Gradually stir the couverture mixture into the buttercream. For the dark chocolate cream, chop 75 g dark chocolate couverture. Prepare as for the light cream (also melt in 160 ml milk, let cool briefly.
Whip 250 g soft butter and 450 g icing sugar, stir in the couverture mixture). Then chill the two creams for about 30 minutes until they are spreadable.
Cut the brownie plate straight all around and quarter it crosswise to form 4 rectangles (each approx. 14 x 18.5 cm). Place a rectangular cake frame around 1 base. Stir the chocolate creams again briefly.
Spread half of the light chocolate cream on top, place the 2nd base on top. Spread with approx. 3 tbsp dark chocolate cream. Place the 3rd base on top. Spread with the rest of the light chocolate cream. 4. lay the base on top. Chill the cake and the rest of the dark chocolate cream for about 2 hours.
Stir the chocolate cream well again. Remove the cake frame carefully. Spread the cream all around the cake. Place the crunchy beads close together on the cake. Dust with gold powder as desired.