To Make the Choux Pastry Dough:

Preheat oven to 190°C / 375°F (210°C / 410°F without fan). Line baking trays with parchment paper or silicone mats.
In a saucepan, combine water, butter, and sugar. Heat over medium until butter melts and mixture begins to bubble.
Remove from heat and add flour all at once. Stir quickly until a dough forms.
Return to heat and stir continuously for 1 minute until a film forms on the bottom of the pan.
Remove from heat and let cool for 10 minutes.
Whisk eggs separately, then gradually add to the dough in portions, mixing well after each addition until smooth and glossy.

To Test the Dough Texture:
7. Dough should be smooth, slightly shiny, and stretch without breaking while holding shape. Adjust with small amounts of egg if needed.

To Pipe:
8. Transfer dough to a piping bag fitted with a 1.2 cm (½-inch) tip.
9. Pipe 10 cm (4-inch) lengths onto prepared trays. Smooth ends with a damp finger.
10. Dust lightly with powdered sugar.

To Bake:
11. Bake for 30–35 minutes until golden brown.
12. Open oven door slightly and let sit for 5 minutes before removing. Cool completely on a rack.

To Fill:
13. Poke two holes in the bottom of each éclair.
14. Pipe in pastry cream or Chantilly cream until filled.

To Glaze:
15. Dip the tops into chocolate sauce, allowing excess to drip off.
16. Let chocolate set before serving.