Step 1: Make the Choux Pastry (Éclair Shells)

1. Preheat oven to 425°F (218°C).
2. In a saucepan, bring water, milk, butter, salt, and sugar to a boil.
3. Add flour and stir vigorously for 1-2 minutes, until a thick dough forms.
4. Remove from heat and let cool slightly (125-135°F, warm but not burning).
5. Add eggs one at a time, mixing fully before adding the next. Stop when the dough is smooth and pipeable but still holds its shape.
6. Transfer dough to a piping bag with a large round tip. Pipe onto a lined baking sheet:
   • Large éclairs: 5-6 inches
   • Medium éclairs: 4-5 inches
   • Small éclairs: 2-3 inches
7. Bake at 425°F for 15 minutes, then reduce to 375°F and bake for 12-20 minutes, until golden brown and hollow.
8. Cool completely before filling.

Step 2: Make the Vanilla Cream Filling

9. In a bowl, whisk together pudding mix and milk for 2-3 minutes, then chill.
10. In a separate bowl, whip heavy cream until soft peaks form, then add powdered sugar and whip to stiff peaks.
11. Fold the whipped cream into the pudding mixture until smooth.

Step 3: Fill the Éclairs

12. Transfer the filling to a piping bag with a round tip.
13. Carefully insert the tip into the cooled éclairs and pipe the filling inside. You may need to fill from both ends.

Step 4: Make the Chocolate Ganache

14. Heat heavy cream in the microwave for 30 seconds.
15. Add chocolate chips and stir until smooth. Heat for additional 10-second intervals if needed.
16. Dip the tops of the éclairs into the ganache. Let set before serving.