In a saucepan, boil water, milk, butter, sugar, and salt.
Add flour off heat and stir until a ball forms.
Cook for 1 more minute, then transfer to a mixer.
Mix to cool slightly, then slowly incorporate eggs until smooth and glossy.
Pipe 6 cm rounds onto a bare iron tray.
Top each with a craquelin disc.
Bake at 165°C (330°F) convection or 190°C (375°F) deck oven until puffed and hollow.
Cool completely.