Beat the eggs with the sugar for about 8-10 min until white and creamy. Mix the flour with the starch and the baking powder, sift over the egg mixture and carefully fold in.
The base is then baked for approx. 20-25 minutes at 180° convection in a 28-cm baking form.
Soak the gelatin in cold water.
For the filling, mix up the egg yolk, Citroback, sugar and milk in a pot, then warm up at medium heat while stirring constantly until the mixture thickens. Then stir in the soaked, squeezed out gelatin until it dissolves. Then strain the mixture with a sieve to remove any lumps of gelatin. Once the mix cools down a bit, add it to the curd in a large bowl and stir until it forms a uniform mass. The stiffly whipped cream is folded in at the end.
Place the bottom half of the sponge base in a cake ring. Add the cream curd mix. Then place the 2nd half of the base on top of it. Leave the cake in the refrigerator overnight so the cream mixture sets.