1. Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.

2. Combine water, butter, and salt in a saucepan; bring to a boil.

3. Remove from heat; stir in flour until the dough pulls from the sides.

4. Return to heat; stir for 2 minutes to dry slightly.

5. Cool slightly, then beat in eggs one at a time until glossy.

6. Pipe 1½-inch mounds on the sheet; smooth peaks with a wet finger.

7. Bake for 20–25 minutes until golden and light; then leave in the turned-off oven ajar for 10 minutes.

8. Cool puffs on a rack.

9. Heat milk and half the sugar; whisk yolks with remaining sugar, cornstarch, and salt.

10. Temper yolks with hot milk; return mixture to the pan and cook until thick.

11. Off heat, stir in vanilla and butter; chill with plastic wrap on surface.

12. Slice cooled puffs; fill with pastry cream and replace tops.

13. Dust with powdered sugar and serve immediately.