Preheat the oven with electrical heat at 150 degrees Celsius.
Separate the eggs so you have the egg whites in one bowl, and the egg yellows in another bowl.
Whip the egg whites to a hard foam.
Whip the egg yellows, the sugar, water and the vanilla sugar together. Add the melted margarine while stirring.
Add the flour and the milk slowly while stirring, and mix it all well.
Fold the egg whites gently in the bowl with the rest of the ingredients, mix gently together.
Pour the batter in a baking form and place the cake in the middle of the oven for one hour.
Take out the cake from the oven and let it rest for three hours before serving it.