The Cake “Karpatka”

Preparation
Preheating the oven and preparing the mold: Preheat your oven to 200°C (thermostat 6-7). Butter and flour a rectangular mold to prepare the baking of the cake.
Preparation of the dough:
In a saucepan, bring the water to the boil with the butter and a pinch of salt.
Off the heat, add the flour all at once and mix vigorously until the dough forms a ball and comes away from the sides of the pan.
Let this dough cool slightly.
Incorporating the eggs:
Add the eggs one at a time to the chilled dough, mixing vigorously after each addition until the dough is smooth and homogeneous.
Spreading the dough in the mold:
Spread half of the batter into the prepared pan, making sure to form an even layer that covers the bottom of the pan.
Preparation of the cream:
In a saucepan, heat the milk with the sugar and vanilla sugar until the mixture simmers.
Meanwhile, in a bowl, whisk the egg yolks with the flour and vanilla extract until the mixture turns white.
Slowly pour the hot milk over the egg mixture while whisking continuously to avoid cooking the eggs.