Boil water, milk, butter, sugar, and salt in a saucepan.
Off the heat, add in cake flour and stir vigorously. Return to medium heat and stir until a thin film forms at the bottom.
Transfer the dough to a bowl and let it cool slightly. Gradually add eggs while beating, until the mixture is smooth and silky.
Pipe the dough onto a baking sheet and dust with powdered sugar thrice.
Bake in a preheated oven at 374°F (190°C) for 20 minutes, then reduce to 347°F (175°C) for another 20 minutes. Let them cool on a rack.