Line baking sheets with baking paper or grease and dust with flour.

Preheat oven to 225°C (435°F) and place an oven-safe bowl of hot water on the bottom rack.

For the choux pastry, bring the milk with butter and salt to a boil in a covered pot.

Sift the flour.

Remove pot from heat, pour in all the flour at once, and stir vigorously with a wooden spoon or dough hook.

Return to the stove and cook the mixture for 1–2 minutes while stirring until it forms a ball.

Let the dough cool.

Gradually add eggs one at a time, waiting 2–3 minutes between each, until the dough is glossy and forms peaks.

Using a spoon or piping bag with a large star tip, pipe tablespoon-sized mounds (about the size of a ping-pong ball) spaced 4 cm apart onto the baking sheets. Chill for 10 minutes.

Sprinkle the pastries with 3–4 tbsp water and bake.

Keep the oven closed for the first 18 minutes. Then reduce the temperature and bake another 7–10 minutes.

Remove the baked cream puffs, let cool on a wire rack, and slice horizontally.

Whip the cream until stiff, sweeten with sugar and vanilla sugar or scraped vanilla bean, and fill the bottom halves.

Place the tops slightly askew and dust with powdered sugar.

Serve soon to prevent the light and crispy pastries from softening.