Preheat the oven to 170℃.
Separate the egg white from the yolk. Grate the the Parmesan with a very fine microplaner.
Mix the egg white, parmesan, flour, water and salt with a hand mixer.
Fill the fishbone mold with the mixture as cleanly as you can. For 4 people you need at least 8 fishbones, but I'd advise to make a few more to not stress about one or two breaking.
Put them in the oven for 8 to 10 minutes. If you're making them for the first time, make sure to keep an eye on them once they're in the oven for 5 minutes. Not every mold might be the same and not every oven is as exact about the temp. You want them perfectly golden.
Take the mold out as soon as the bones are perfectly golden. Put it down for 30 seconds and then carefully remove the fishbones from the mold and put them on a sheet of baking paper.
Spray the outside of the fishbones golden with your goldspray for baking.