Mix the eggs, sugar and salt until the mixture is very fluffy. It is worth while spending a bit of time to ensure that the mixture is a fluffy as possible as it influences the consistancy of the pastry.
Let the milk, butter and vanilla sugar come to a boil and then mix immediately with the eggs/sugar mixture to get a homogeneous mixture.
Let the mixture first cool to room temperature and let it rest in the fridge for 8 - 24 hours (depending on how much time you have).
Stir through the mixture before equally dividing into the little cannelés forms. Let them bake for about 45 minutes at 180 degrees. They should be dark brown on the top. Let them cool completely before serving - on the same day.