Separate eggs. Beat the egg white with the sugar until the sugar is dissolved. Stir in the egg yolks. Sift the flour, starch and baking powder on top and fold in. Put them into a springform pan and bake at 160° for about 45 minutes.
Allow to cool and cut through twice horizontally (the top shelf is not required, however). Place the bottom cake layer on a cake plate. Place a cake ring around it.
Soak the gelatine. Cover the lower bottom with mandarins. Whip the cream with the sugar until stiff. Stir in the sour cream and lemon juice. Dissolve the gelatine and fold in. Pour half of the cream onto the mandarins.
Place second shelf on top. Cover this with mandarins as well.
Add the rest of the sour cream and smooth it down. The cake is best left to cool overnight. Decorate with cream patches, tangerines and pistachios.