Separate eggs. Beat egg white and salt until stiff. Mix egg yolk and sugar until creamy and fold into the beaten egg white. Mix flour, cornstarch and cocoa. Grease the bottom of a springform pan (16 cm Ø) and fill in the dough.
Bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for about 20 minutes. In the meantime, soak the gelatine in cold water. Whip 300 g whipped cream with the whisks of the hand mixer until stiff, add vanilla sugar bit by bit.
Squeeze and dissolve the gelatine. Fold gelatine into the cream. Drain wild cranberries and, except for 4 teaspoons for decoration, fold into the cream. Cut the sponge cake base horizontally twice.
Spread the lower base with half of the cranberry cream. 2. place the base on top, press down lightly and spread with the rest of the cranberry cream. Cover with the 3rd base. Whip the rest of the cream until stiff.
Fill a small part for decoration into a piping bag with star-shaped spout. Spread the rest of the cream on the cake. Spray the cream dab onto the cake. Decorate with remaining cranberries and chocolate flakes.
Sprinkle the cake rim with chocolate flakes.