About this recipe:The pastry will make 24 medium buns, 15 large éclairs, or 36 profiteroles. This recipe looks long but that's only because the methods are precisely detailed - it's not difficult to make! See tips for flavouring options and a gluten free chocolate choux option. Crème pâtissière is 15 minutes preparation and 90 minutes chilling; pastry is 30 minutes preparation and 30 minutes baking; ganache is 5 minutes preparation; assembly is 20 minutes.
Whisk the sugar, egg yolks, and cornflour together in a medium bowl until frothy and pale.
Bring the milk and vanilla to the boil on the hob, then immediately remove from the heat. Pour a large spoonful of the hot milk over the yolk mixture, whisking constantly; repeat 4 times, then whisk in the rest of the milk until well combined. Return the mixture to the pan over a very low heat, whisking all the time, for 3 to 4 minutes or until it thickens to a stiff custard consistency (but don't allow it to come to the boil again).
Remove the pan from the hob, add the butter, and whisk vigorously until the butter is melted and well combined. Pour back into the bowl and cover with cling-film (push it down so it touches the whole surface of the cream to avoid a skin forming). Leave to cool until it can be put into the fridge to chill fully.
For the gluten-free choux pastry:
Preheat oven to 220 C / Gas 7. Place an oven-safe container (such as a large ramekin or mug) in the bottom of the oven. This will be filled with water later for steam whilst baking.
Cut two sheets of baking parchment to fit two baking trays and draw onto them a total of 24 circles 5cm (2 in) wide for buns, 15 lines 15cm (6 in) long and 5 cm (2 in) wide for éclairs, or 36 circles 2.5 cm (1 in) wide for profiteroles, leaving room for expansion during baking. Turn the papers over (ensure you can see your markings through) and set aside. Note: drawing isn't required, but it can help with even placement of the pastry.
Heat the water, butter, and sugar on the hob over a medium heat until the butter is fully melted and bubbles are forming at the edges. Take the pan off the heat and tip the flour in all at once, beating vigorously with a wooden spoon until combined. Note: It may look like big unworkable blobs sitting in excess melted butter, but do not worry, it will come together with the eggs in the next step.
Return the pan to the heat and cook for 2 to 3 minutes, beating constantly, until it's mostly one ball coming away from the sides of the pan. Remove from the heat and allow to cool for 3 to 4 minutes before adding the beaten egg some at a time, beating well between each addition. You want a thick (not too creamy) dough - you may not need all the egg.
Transfer the mixture to a piping bag with a 1/2" nozzle (or simply cut the tip of a piping bag to 1/2" width). Lay your papers on your trays (with markings underneath, if using). Pipe into your circles or onto your lines to a height of about 5cm (2 in), smoothing the tops with a damp finger to remove bumps if you like. Note: If you're not making éclairs and don't want to pipe, try an ice cream scoop, or just use your fingers to drop blobs in place. (The recipe picture shows buns not piped and not smoothed, for a rustic look.)
Place the trays into the oven, and pour cold water into the container at the bottom. Bake for 5 minutes, then carefully remove the water container. Bake for 15 to 20 minutes further (smaller buns will be faster), turning trays halfway through for even baking, until risen and golden brown, and a tap on the bottom of a couple of buns sounds hollow.
Remove the trays from the oven and poke a hole in the bottom of each bun with a skewer or the tip of a sharp knife. Turn each bun on its side and return trays to the oven, turn oven off, and leave for 4 to 5 more minutes until crisp. Remove trays from the oven and move buns to a wire rack to cool.
For the chocolate ganache:
Bring the cream (and sugar if using) to the boil on the hob, then remove from the heat. Add the chocolate pieces and whisk briskly until fully melted and the ganache is glossy. Pour into a small, wide bowl, and leave to cool.
To assemble, using a piping bag with a long thin nozzle, or a jam syringe, pipe the crème pâtissière into the buns from the bottom (if making éclairs, you'll want to make 2 holes, one at each end, to ensure the cream fills it fully). Spread the ganache over the top of each bun, or, dip the tops and lift up with a twist.
Gluten free chocolate choux:
For a gluten free chocolate choux pastry: Add 40g cocoa power with a reduced amount of 130g gluten free (or rice) flour. Watch carefully whilst baking due to the dark colour of the dough.
You can add 2 teaspoons peppermint or almond extract, or the finely grated zest of one orange. Use white chocolate (reduce double cream to 75ml and don't add sugar) for the ganache with a chocolate choux pastry for a great alternative which looks stunning.