Preheat the oven to 170C fan (190C non fan) Put the water, milk, butter 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 or wooden spoon 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 2 centimetre open star French piping 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 8 eclairs, 12 centimetres long, onto the baking sheet - leaving at least a 5 centimetre gap between them.
Put the baking sheet into the hot oven and cook for 30 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 so that steam can escape. Put them back into the oven, upside down, for 5 minutes then straight onto a wire rack to cool.
Once the eclairs have cooled, slice the top off the Camembert and scoop the creamy filling into a piping bag fitted with the same piping tip.
Slice the eclairs lengthways along one edge, with the ‘hinge’ lower down on one side, and the cut higher up on the other. Carefully pipe Camembert into the eclairs.
With the remaining Camembert, cut eight thin slices and press them carefully on top of each eclair. Load them up with caster sugar and use a blow torch to brulee the top. Leave to cool and then serve.