Season the squid and fish and then sink in the egg beaten with a teaspoon of water.
Mix the potato starch with the flour and pass the squid and fish through it as well.
Preheat the oil to high temperature and fry in small batches. Be careful that there's nothing with water close by and also keep children away.
When you take them out of the oil put them in a bowl with kitchen paper so it absorbs the excess oil.
Whisk together the egg, salt and mustard.
Add the oil slowly while whisking. Stop when you like the consistency.
Finish with a few drops of lemon juice, the chopped pickles and egg white.