Mix eggs with 170 grams of sugar and one package of vanilla sugar. Beat with a mixer until the volume increases 3-4 times.
Add flour little by little into the mixture with eggs and sugar, carefully mix the dough with a spatula from bottom to top so that the dough does not lose its airiness.
Line a baking pan with parchment and grease with oil, pour in the dough and twist a little so that the dough is evenly distributed. Bake in an oven preheated to 180 degrees for 35-40 minutes. Do not open the oven until the biscuit is ready.
While the biscuit is baking, make the cream. Mix cottage cheese, sour cream and remaining sugar in a blender; add banana if desired. If you don't have a blender, grind the cottage cheese through a sieve. Cut the finished sponge cake into 2 parts in the middle to make 2 layers. Grease the first cake with curd cream, cover with the second and brush the top and edges with cream.
Serve the sponge cake with chopped fruit or berries. Garnish with almonds and a sprig of mint or lemon balm.