Melt butter and heat water and milk. In a medium saucepan, add the water, milk, butter, sugar and salt, and heat on low until the butter is melted and the sugar has dissolved. Increase the heat to medium to high and bring to a rolling boil.
Add flour. Remove the pan from the heat and add the flour immediately. With a wooden spoon, mix together vigorously until completely combined.Then return to medium-high heat and beat for 2 minutes until the mixture comes away from the sides of the pan and forms a ball. You’ll see a film form on the base of your saucepan, and you’ll know it’s ready. (Use a digital thermometer for accuracy- the panade should be between 75°C to 80°C (165°F and 175°F)
Beat to release steam. Remove the pan from the heat and place it in the bowl of a stand mixer fitted with the paddle attachment. Beat for 1 minute on low speed to release some steam. Use a digital thermometer for accuracy- the panade should get to 60°C (140°F) or under before continuing on with the next step.In a small jug, whisk the four eggs together.
Add the eggs to make the choux dough
Please read this step before continuing as the amount of egg added can vary.With the mixer running on low speed, slowly pour in ¾ of the whisked eggs in 3 to 4 separate additions, mixing for 30 seconds between each addition. Scrape the sides and base of the bowl halfway through. It may look curdled and slimy to start with but will come together as you beat the mixture. Once the eggs have been fully incorporated, beat the mixture for a further 2 minutes.Note on the perfect consistency. The choux pastry should be smooth and shiny and should hold its shape when a finger is passed through the mixture. Another sign that the batter is ready is when the beater or a rubber spatula is pulled up out of the batter and a thick V-shaped ribbon forms, of smooth dropping consistency. If your pastry has not achieved this consistency, add the remaining egg a teaspoon at a time and test the consistency again. If you need more egg, then whisk the 5th egg in a small bowl, and add a tiny bit at a time. Stop adding the egg as soon as you get the right consistency. I doubt that you'll need all this egg. Set aside any remaining egg to be used as egg wash.
Chill, pipe and bake
Chill the dough. Preheat the oven to 200°C (390°F). Fill a piping bag fitted with a round piping tip and close the open end of the piping bag and refrigerate for 30 minutes Preheat the oven to 200°C (390°F).Pipe choux onto the baking tray. Line a large baking tray with parchment paper. Whilst holding the piping bag upright and keeping the tip of the piping tip touching the choux pastry, pipe 4cm (1.5-inch) wide mounds onto the prepared tray. Keep them 2.5cm (1-inch) apart.
Prep choux on the tray.Using a pastry brush dipped in water, brush the parchment paper around the mounds. The water creates steam in the oven, which helps puff up the choux.Using the tip of your finger dipped in water, smooth the points of each mound. This stops the peaks from burning in the oven. Add milk to the remaining egg and whisk together. Brush this egg wash gently over the top of the choux pastry mounds.
Bake. Place the tray in the oven and immediately reduce it to 180°C (350°F) and bake for 25 to 30 minutes, or until golden brown and crisp. It's important that you do not open the oven door in these first 25 minutes of baking. Remove the buns from the oven and skewer a hole in the bottom of each choux bun to allow the steam to escape. Return to the oven for 5 to 10 minutes, and then allow to cool completely on the baking tray.
Assemble. Slice in half or pipe into the centre your favourite filling.
Step-by-Step Photos: My blog post includes helpful step-by-step photos to help guide you through making this recipe.To store: Store unfilled choux pastry shells in an airtight container for up to 2 days at room temperature, or in the refrigerator for up to 5 days. Re-crisp the shells in a hot oven for 5 minutes.If the shells are filled, then they are best eaten within a couple of hours, or stored in an airtight container and refrigerated for up to 2 days. Please note though, that the choux pastry will soften.To freeze: Unfilled choux pastry shells can be frozen in a freezer-safe container for up to 2 months. Thaw in the refrigerator overnight and re-crisp in a hot oven for 5 minutes.Tip 1:Weigh your ingredients: For this type of recipe that relies on the accuracy of correctly measured ingredients - I strongly recommend using digital scales.Tip 2: Add eggs in gradually rather than all at once. You can then control how much is needed to achieve the perfect consistency. Remember - Too little egg = you can add more. Too much egg = dough is ruined.Tip 3:Hold the piping bag upright. When piping the buns, hold the bag upright to make the buns as round as possible.Tip 4:Don't open the oven door. The steam within the oven helps the choux pastry puff up. If that steam gets released along with the newly introduced cold air, before the choux buns have had a chance to set in their puffed shape, then they'll deflate.Trouble Shooting Tips: Please read the blog post for an in-depth look into troubleshooting tips.