Finely chop the gherkins and capers. Finely chop the chives and parsley leaves. Finely dice shallot. Finely chop the hard-boiled egg or dice with the egg cutter.
Put the raw eggs, some salt, mustard and some cucumber water in a mixing bowl and whip until creamy with a hand blender. Add vegetable oil in a thin stream and mix in. Finally, withhold the olive oil. Season with salt, pepper and lemon juice.
Fold in the gherkins, capers, shallots and cubed eggs and season the tartar sauce again if necessary.