Preheat your oven to 200C and line a baking tray with baking paper.
Whisk together your flours and set them aside. Weigh out your eggs into a small jug and whisk them well.
Combine the milk, water and butter in a small saucepan and place it over a medium heat. Allow the butter to melt. When the milk begins to bubble, add in the flour and whisk vigorously until everything is well combined. It won’t form a smooth paste like regular choux, but it will clump up and start to look like dry mashed potatoes. Grab a wooden spoon and continue mixing for up to 30 seconds to continue cooking off liquid.
Remove the pan from the heat and allow to cool to a hand comfortable temperature so you don’t scramble the eggs in the next step.
Add the egg a little at a time and stir really well until each batch of egg incorporates. It will look like the egg will never incorporate, but keep mixing and I promise it will. Repeat with the next bit of egg.
The tricky thing with choux pastry is that the amount of egg needed generally differs from batch to batch. The dough should look like firm but silky mashed potatoes with added cream. It should be a little shiny and still firm enough that it will hold shape when you pipe it. If in doubt, don’t add more egg. Too much egg will result in flat disks of choux as opposed to air filled round puffs of choux. Some batches will require the whole 125g, some only 100g (or less!). This depends on everything from the different batches of flour to the humidity in your kitchen. It’s something you will learn with experience.
When you’re happy, transfer your choux pastry into a piping bag or a ziploc bag with a tiny cut in a corner (which will be your piping nozzle).
Pipe 7-8 rectangular logs (approximately 10cm x 3cm) or 10-11 golf ball sized puffs. I like to pipe a couple of layers upwards to give them a bit of height. They should hopefully be holding their shape – if not, you might have added a bit too much egg (but bake them anyway!)
Bake at 200C for about 15-20 minutes or until they have puffed up and become golden.
Turn the oven down to 150C and bake for an additional 10-20 minutes or until the choux are completely dry. You might like to lightly tent them with a piece of foil if they’ve turned sufficiently golden.
Working quickly, use a skewer to poke one small air hole on the side of each choux. I use a bamboo skewer for this. This will prevent your pastries from collapsing as they cool. Allow them to cool completely on the tray.