Bring water, salt and butter to a boil. Add flour, stir until smooth. When the dough comes off the wooden spoon, let it cool over and beat in the eggs with a mixer. Use the dough immediately!
Pipe doughnuts or swans on top. Bake at 220 °C for 10 minutes and at 180 °C for another 15 minutes.
In the meantime, whip the cream with vanilla sugar and cream stiffener until stiff.
Remove the finished swan from the oven. Protect it from drafts while it cools down.
Fill the swan and sprinkle with powdered sugar.