Place a baking stone on the centre rack of the oven, and preheat to 220c/200c fan.If you don’t have a baking stone, a baking sheet or two will also work.
Place water, milk, salt, sugar, and butter into a saucepan, and set over a medium heat. Bring the mixture to the boil.
In the meantime sift the bread flour, and crack your eggs into a jug and lightly whisk.
When the mixture reaches the boil, remove from the heat, and stir in the flour, all at once. Incorporate completely, and then return the pan to the heat, stirring continuously for 3 minutes. After the 3 minutes are up, put the dough into a clean bowl. Do not scrape out any film on the pan.
Beat in the eggs gradually, either by hand, or by using the help of a machine. The easiest method is to use a food processor and pour the eggs down the feeling tube. Allow the pastry to cool to 25c-30c before piping.
Pipe 10cm (4-inch) eclairs into a lined baking sheet using a french star tip. You’ll want the eclairs to be about 2cm (3/4 of an inch) wide.
Brush with a little melted butter, and use the pastry brush to smooth over any peaks. You can also use the pastry brush to coax any wonky eclairs back into shape.
Place the baking tray directly onto the baking stone.Once the oven door is closed, immediately lower the temperature to 200c/180c fan
After 30 minutes, check if the eclairs are completely firm.If not, continue baking a little longer.
Remove the eclairs from the oven, and turn the oven off. Use a skewer to poke two holes in the end of each eclair. Use the skewer to stir around inside a little, to help create a nice clean space for the filling.
Use a bismark tip, or small french star tip, to create 2 larger holes in the base of each eclair, then place them back on the baking sheet, upside down.
Place the eclairs back inside the still hot oven, to help dry out the inside of the eclairs - this will take about 5 minutes
Transfer the eclairs onto a wire rack and leave to cool completely.