Preheat the oven to fan 180C/conventional 200C/gas 6. Fold a sheet of greaseproof paper in half and then unfold to leave a crease. Sift together the flour and salt onto the paper twice. Put the butter and water in a pan and bring to the boil. Remove from the heat and tip the entire flour and salt mixture into the pan. Reduce the heat to low and return the pan to the stove. Beat the mix with a wooden spoon or electric mixer over a low heat until it comes away easily from the sides. Leave to cool for 10 minutes. Beat in the eggs a little at a time, mixing until smooth yet strong enough to stand in peaks. You may not need all the egg.
Pipe the choux into thick eclair strips (10-12cm long and 1.5cm wide) on a non-stick baking tray, leaving a space between each. Bake for 20-25 minutes until lightly golden and crisp to the touch. Remove from the oven and leave to cool. You can make the eclairs up to this stage the day before and keep them in an airtight container, or they can be frozen.
Halve the passion fruits and scoop the pulp into a small pan. Add the sugar and bring to a simmer. Cook gently for a minute or two until a thick consistency is reached. Leave until cold, then spoon the syrup into the custard, saving a little to finish the dish.
Whip the cream to soft peaks before gently spooning into the flavoured custard. Refrigerate until needed (it will keep for up to 4 hours).
To serve, split the eclairs lengthways and put the bases on individual plates. Spoon on the cream generously – it will happily tumble onto the plate. Now sprinkle the raspberries over and around, and drizzle with the passion fruit syrup. The lids can now be placed on top and dusted with icing sugar.