To make the hash browns, mix the grated potato with the salt then set in a strainer over a bowl. Allow to potatoes to drain for up to 4 hours (the longer the better) until they have released most of their moisture.
Allow the starch to settle at the bottom of the bowl of liquid then pour off the liquid, then reserve 1 tablespoon of potato starch.
Mix the egg with the starch then mix in the grated potato, salt and pepper.
Heat a generous glug of oil in a non-stick frying pan then form the potato mixture into cakes and fry for 10-15 minutes until golden brown, crisp and cooked through.
Drain on kitchen paper.
To make the hollandaise, blend the eggs and lemon juice in a blender until pale and frothy. Slowly drizzle in the hot, melted butter until the sauce is completely emulsified. Season with more lemon (if required), salt and pepper. If the sauce is too thick, add a few teaspoons of boiling water and blend until the consistency is to your preference.
To serve, top the hashbrowns with rocket, ham of your choice, poached eggs and finish with a generous spoonful of hollandaise.