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

2. In a saucepan, combine water, butter, and salt. Heat until butter melts and mixture comes to a gentle boil.

3. Add flour all at once. Stir vigorously until a smooth dough forms and pulls away from the pan (about 1–2 minutes).

4. Transfer dough to a bowl and cool for 5 minutes (it should be warm, not hot).

5. Add eggs one at a time, mixing well after each. Dough should be smooth, glossy, and pipeable.

6. Spoon dough into a piping bag (or use a spoon) and pipe 12–15 small mounds onto the baking sheet, spaced apart.

7. Bake 25–30 minutes until puffed and deep golden. Do NOT open the oven during baking.

8. Turn oven off, crack the door open slightly, and let puffs sit 5 minutes to help prevent collapsing.

9. Cool completely on a rack.

10. Make filling: whip cold heavy cream with powdered sugar and vanilla to soft peaks.

11. Gently fold in pistachio paste until smooth and evenly colored.

12. Fill puffs: slice in half or poke a hole and pipe filling inside.

13. Garnish with powdered sugar and chopped pistachios. Serve chilled or at cool room temperature.