Preheat your oven to 180°C (convection/fan-assisted).
In a medium saucepan, combine the milk, water, butter, salt, and sugar. Bring to a boil over medium heat.
Remove from the heat and immediately add the flour. Stir vigorously with a spatula until a dough forms.
Return the pan to medium heat and cook for about 2 minutes, stirring constantly, until the dough dries out slightly and pulls away from the sides. A thin film will form at the bottom of the pan.
Transfer the dough to a stand mixer fitted with the paddle (K-beater) attachment. Mix on low speed for 2 minutes to cool the mixture slightly.
Lightly beat the eggs and add them in 4 portions, mixing well after each addition.
The final dough should be smooth, shiny, and pipeable.