Separate eggs. Beat the egg white and 3 tbsp. water until stiff, adding 100 g sugar and salt. Stir in egg yolks. Mix flour, starch and baking powder, sieve over the mixture and fold in. Put the sponge cake into a greased springform pan (approx. 26 cm Ø) and bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 20 minutes.
Remove the sponge cake from the oven and let it cool down on a cake rack. Roughly chop the chocolate. Melt 5 tablespoons of cream and chocolate in a bowl over a warm water bath, then let it cool down a little.
Soak gelatine in cold water. Melt 5 tbsp. liqueur and gelatine in a small pot, then mix with 200 ml liqueur and chill for about 20 minutes until the liquid starts to gel.
Remove the sponge cake from the mould and cut through horizontally 2 times. Place a cake ring around the lower cake base and spread the chocolate on the cake base. Place the cake base in a cool place for about 5 minutes. Spread the gelled liqueur on the chocolate layer and chill for about 2 hours.
Whip 400 g cream and 5 tbsp. liqueur until stiff, adding vanillin sugar and 1 tbsp. sugar. Fold in hazelnuts. Place the middle sponge cake base on the liqueur layer and spread the hazelnut cream on top.
Finish with the sponge cake lid and chill the cake for at least 1 hour.
Whip 300 g cream until stiff. Remove the cake from the cake ring and spread with approx. 2/3 of the cream. Fill the rest of the cream into a piping bag with star-shaped spout. Sprinkle the edge with brittle. Spray cream in tuffs onto the cake and decorate with hazelnuts.
Refrigerate the cake until serving. Just before serving, spread 5 tablespoons of liqueur on the cake.