How to make
Put the milk on the stove, but set aside 1/2 cup (100 ml) of it, add the sugar and vanilla and wait for it to boil.
Separate the yolks, put them in a bowl along with the flour and with the milk, that you set aside, beat them well with a mixer.
Beat the egg whites into a foamy mixture and add a pinch of salt to it.
When the milk boils, carefully add the mixture with the beaten yolks, while stirring constantly, so that it doesn't lump up.
Boil the confectionery cream for another 5 minutes until the desired density is obtained.
Once it has cooled, the classic cake cream will thicken even more.
Add the butter to the hot cream and stir until it has completely melted.
Add the whipped egg whites to the almost ready cream and mix gently with a spatula, until you have a homogeneous mixture, but make sure it stays fluffy for the Napoleon cake cream.
Wait 10-15 minutes for the cream to set, so that it does not run down on the side of the prepared Napoleon cake, and spread the cake layers with it generously.
