Preheat your oven to 180 °C // 356 °F top/bottom heat and separate the eggs into two separate bowls.
Take the bowl with the egg yolks and add half of the superfine sugar and the entire vanilla sugar.
½ cup Superfine sugar, ¾ tablespoon Vanilla Sugar, 6 Egg yolk
Beat the ingredients with an electric mixer until very foamy and set aside.
Grab the bowl with the egg whites and add the second half of the superfine sugar. Beat them until very stiff.
6 Egg white, ½ cup Superfine sugar
In the mixing bowl with the beaten egg yolks, gently fold in the stiffly beaten egg whites. Then sift the flour over it and mix it in
1 cup Cake Flour
Fill the batter into the springform pans (about three-quarters full) and put the filled springform pans in the oven.
Bake on the middle shelf for half an hour.
Remove the springform pan(s) from the oven and let cool for 15 minutes.
Before opening the springform pan, cut along the edge once with a sharp knife to ensure no dough sticks to the sides.
Take the dough out of the springform pan and let it cool further on a cooling rack.
Once the dough is no longer warm, take the first sponge cake and cut it in half. Do the same with the second sponge.