Choux pastry: Boil water with butter and salt in a saucepan. Add flour all at once and stir vigorously until the dough comes away from the bottom of the pot. Let it cool down a bit.
Stir in eggs one at a time until a smooth, shiny batter is formed.
Halve the dough. Spread the first half on a baking tray covered with baking paper and bake in a preheated oven at 200 °C for about 25 minutes until golden brown. Repeat with the second half.
Vanilla cream: Cook 500 ml of milk with pudding powder and sugar to a thick pudding. Let cool. Cream butter with vanilla sugar, stir in pudding a tablespoon at a time until smooth.
Spread the cream on the first dough base and place the second base on top.
Dust with powdered sugar and chill for at least 2 hours.
