1. Preheat the oven to 425°F with a rack positioned in the middle.

2. In a medium saucepan , combine 120 ml water , 120 ml whole milk , 115 g unsalted butter (cut into cubes), 10 g granulated sugar , and 5 g salt .

3. Place the saucepan over medium heat and stir occasionally until the butter is melted and the mixture comes to a simmer.

4. Remove the pan from heat and immediately add 150 g all-purpose flour all at once. Stir vigorously with a wooden spoon until the flour is fully incorporated and no dry flour remains.

5. Return the saucepan to medium heat and cook, stirring constantly, until the dough forms a ball and a thin film forms on the bottom of the pan, about 2 minutes .

6. Transfer the dough to a stand mixer bowl fitted with a paddle attachment. Let the dough cool slightly for 5 minutes , stirring occasionally to release steam.

7. With the mixer running on medium speed, add 4 eggs (large, at room temperature) one at a time, ensuring each egg is fully incorporated before adding the next. The dough should be smooth, glossy, and form a V-shaped ribbon when lifted with a spatula.

8. Transfer the choux pastry to a piping bag fitted with a large round tip (or cut a 1.5cm opening if using a disposable bag).

9. Line a baking sheet with parchment paper. Pipe the dough into your desired shapes, leaving space between each piece as they will expand during baking.

10. For cream puffs, pipe 4cm rounds about 5cm apart. For éclairs, pipe 10cm long strips about 5cm apart.

11. Use a finger dipped in water to smooth any peaks on the piped dough.

12. Bake at 425°F for 15 minutes , then reduce the temperature to 350°F and continue baking for 15-20 minutes until the pastries are golden brown and feel hollow when tapped.

13. Turn off the oven, crack the door open, and let the pastries cool in the oven for 15 minutes to prevent them from deflating.

14. Remove from the oven and let cool completely on a wire rack before filling.