Line the bottom of a springform pan (26 cm Ø) with baking paper. Separate the eggs. Beat the egg whites, 2 tablespoons of water and 1 pinch of salt until stiff, while adding 125 g sugar and 1 packet of vanilla sugar. Fold in the egg yolks one at a time.
Sift flour, cocoa and baking powder on top and fold in. Brush into the mould. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) for 20-25 minutes. Let them cool down.
Cut the sponge in half horizontally. Close a cake ring around the lower cake base. Soak 4 sheets of gelatine in cold water. Whip 400 g cream until stiff, adding 50 g sugar and 1 packet of vanilla sugar.
Heat 50 ml advocaat. Squeeze out the gelatine and dissolve in it. Stir in 2-3 tablespoons of stiff cream and then fold into the remaining stiff cream. Spread on the lower base. Place the second base on top and chill for about 2 hours.
Whip 250 g cream until stiff. 1⁄3 Spread the cream on the cake. Fill another third into a piping bag with a small perforated spout and squirt a dotted edge onto the cake.
Soak 2 sheets of gelatine in cold water. Heat 150 ml of liqueur, squeeze the gelatine and dissolve in it. Let cool for about 5 minutes and spread on the cake. Coarsely chop the chocolate coating, fill into a freezer bag, close the bag.
Melt in hot water. Cut off a very small corner at the bottom and decorate the liqueur layer with it in circles. Chill for about 2 hours.
Remove the advocaat cake from the cake ring. Spread the cake ring with the remaining cream and press the chopped pistachios on.