First prepare the choux pastry. To do this, boil the butter in pieces with 250 ml of water and salt in a saucepan.
Once melted, add the flour all at once. Stir vigorously with a wooden spoon until a lump is formed and a white coating can be seen on the bottom of the pot.
Transfer the batter to a mixing bowl. Stir one egg at a time thoroughly into the warm batter with the dough hook of the hand mixer.
Pour the mixture into a piping bag fitted with a large star nozzle.
Preheat the oven to 200 °C (180 °C convection oven).
Spray twelve rosettes on a baking tray with baking paper, spacing them well apart. Place the tray in the oven (center), pour a cup of water on the bottom of the oven (or on a second baking tray that has also been heated on the lowest rack) and quickly close the oven door.
Bake the cream puffs for 20-25 minutes until golden brown (do not open the oven door!).
Remove, cut a lid off each one, and let cool on a cooling rack.
For the filling, whip the whipped cream with sugar and vanilla sugar until stiff and pour into a piping bag fitted with a large star nozzle.
Fill the bottom halves of the cream puffs with the vanilla cream. Put the lids on and sprinkle the cream puffs with powdered sugar.
Preparation Tip:
The cream puffs can be filled with other fillings to taste.