Wash the potatoes and cook in boiling water for about 20 minutes. Rinse the potatoes under cold water and remove the skin. Let the potatoes cool down for about 1 hour, grate roughly and weigh 375 g. Separate the eggs. Mix egg yolks and sugar with the whisk of the hand mixer for about 5 minutes until creamy. Stir in potatoes. Mix hazelnuts, semolina and baking powder, add and stir in.
Beat egg white until stiff and fold in. Line the bottom of a springform pan (26 cm Ø) with baking paper. Fill in potato mixture and smooth it down. Bake in the preheated oven, 2nd shelf from below (electric oven: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 50 minutes. Let the cake cool down in the tin on a cake rack for at least 4 hours. Remove from the tin and remove the baking paper. Cut the cake 2 x horizontally. Whip 400 g cream, cream firmer and vanilla sugar until stiff. Spread half of the cream on the lower cake base and cover with the middle cake base. Spread the rest of the cream on top and cover with the third cake base. Cover the cake and leave it to cool overnight. Cut the chocolate into fine rolls with a peeler. Cut the marzipan into 12-16 equally sized pieces and shape them into balls. Sieve 2 tablespoons of cocoa into a deep plate and roll the balls in it.
Whip 400 g cream, cream firmer and vanilla sugar until stiff. Spread half of the cream on the lower cake base and cover with the middle cake base. Spread the rest of the cream on top and cover with the third cake base. Cover the cake and leave it to cool overnight. Cut the chocolate into fine rolls with a peeler. Cut the marzipan into 12-16 equally sized pieces and shape them into balls. Sieve 2 tablespoons of cocoa into a deep plate and roll the balls in it. Whip 600 g cream until stiff. Put half of the cream in a piping bag with a large star-shaped spout and chill. Spread the remaining cream all around the cake. Press the chocolate rolls to the edge and sprinkle them over the cake. Sprinkle lightly with cocoa. Spray 12-16 tuffs onto the cake and decorate each with a marzipan potato. Keep cool until serving
Whip 600 g cream until stiff. Put half of the cream in a piping bag with a large star-shaped spout and chill. Spread the remaining cream all around the cake. Press the chocolate rolls to the edge and sprinkle them over the cake. Sprinkle lightly with cocoa. Spray 12-16 tuffs onto the cake and decorate each with a marzipan potato. Keep cool until serving
Waiting time approx. 17 hours