1. In a saucepan over medium heat, combine water, butter, and salt. Bring to a boil.

2. Reduce heat to low and add flour all at once, stirring vigorously until the mixture forms a ball.

3. Remove from heat and cool for 5 minutes. Add eggs one at a time, beating well after each addition until the dough is smooth and glossy.

4. Preheat oven to 400°F. Pipe or spoon dough onto a parchment-lined baking sheet.

5. Bake for 25–30 minutes or until golden and puffed. Let cool completely.

6. In a separate saucepan, whisk milk, sugar, cornstarch, and a pinch of salt.

7. Heat over medium, stirring constantly until thickened.

8. Remove from heat and stir in vanilla extract. Let cool and refrigerate for at least 1 hour.

9. Slice tops off puffs or poke bottoms and pipe in chilled custard filling.

10. Dust with powdered sugar if desired, and serve.