In a saucepan, combine butter, salt, sugar, and cold water. Heat over low to medium heat until the butter melts and the mixture starts to boil.

Turn off the heat and sift cake flour into the saucepan. Quickly mix until combined.

Return the saucepan to low to medium heat and cook the mixture for 50–60 seconds until a white film forms at the bottom.

Transfer the dough to a bowl and gradually add beaten eggs, adjusting the consistency.

Fill a piping bag with the dough fitted with a round nozzle.

Pipe the dough into 2cm diameter circles. Spray water generously on the surface and smooth out any peaks with your finger.

Bake in a preheated oven at 180°C for 13–15 minutes. Avoid opening the oven during baking.

[Ganache] Heat heavy cream in a saucepan until just before boiling (bubbles appear at the edges).

Pour the heated cream over finely chopped dark chocolate and mix until smooth.

Chill the ganache in the refrigerator until it reaches a usable consistency.

Poke a hole in the bottom of each choux pastry using a chopstick.

Fill a piping bag with the ganache and carefully fill each choux pastry.