Make the creme patissiere: put the milk into a saucepan and bring it to the boil, then take it off the heat and let it cool for a few minutes.
Meanwhile, put the eggs and sugar into a large mixing bowl and whisk them together, then add in the flours and vanilla and mix them through.
Tip the hot milk into the egg mix, mix it all together then return the whole mixture to the saucepan over a low heat, and use the whisk to stir constantly while you bring it to the boil. Once the custard has reached a boil and thickened, remove it from the heat and put it into a bowl. Put clingfilm right on top of the custard to stop it forming a skin, seal it around the edge of the bowl, and chill until needed.
Make the eclairs: preheat the oven to 170C fan (190C non fan) Put the water, milk, butter, sugar and salt into a saucepan and bring to the boil, then remove from the heat.
Sieve the flour, then tip it into the milk mixture and mix it vigorously with a wooden spoon, to bring it together.
Return the pan to the heat for 2 minutes, stirring constantly, then take it off the heat and let it cool for 2 minutes while you prepare the eggs.
Break the eggs into a large mixing bowl, then tip in the pastry mix and beat it all together with a whisk until it’s smooth. You should be able to run your finger through it and for it to hold its shape.
Transfer the pastry mix into a piping bag fitted with a 1cm open star tip.
Secure a piece of non stick baking paper onto a baking sheet by piping a small amount of pastry under each corner of paper.
Pipe 12 eclairs 10cm long onto the baking sheet, leaving at least 3 cm between them. Each eclair should be 1.5cm wide
Put the baking sheet into hot oven and cook for 20 minutes, after which the eclairs should have risen and turned golden brown. Use a chopstick to make three small holes, evenly spaced, along the bottom of each eclair. Then put them straight onto a wire rack to cool.
Fill and top the eclairs: once the eclairs have cooled, put the creme patissiere into a piping bag fitted with a 1cm round tip. Pipe the custard into each eclair through the holes in the bottom of the eclair.
Take a walnut-sized piece of fondant icing and roll it out with your fingers so that it’s almost as long as the eclair, then squash it into a thin strip about 2 cm wide. Top each eclair with a piece of icing, and gently press it down to stick it on. Use a small blowtorch to heat the icing so that the sugar melts - be very careful not to burn the delicate pastry. The sugar will bubble and turn brown. Do this for each eclair, let them cool for 10 minutes, and then serve.
Serving the eclairs: eclairs are best fresh so serve them as soon as the icing has cooled and crisped up. If you don’t serve them straight away, you might have to blowtorch the sugar again to crisp up the sugary topping.