For the brine, dissolve the salt in the water in a large pan, then add the ham hock and soak for 24 hours. Drain, then rinse and soak in a large pan of fresh water for another 24 hours.
Place the brined ham hock, the pig's trotters and the pig's ears into a large pan along with the cooking liquid ingredients (the chicken stock should just cover). Bring to the boil and skim off any scum that rises to the surface, then simmer for 2 hours and 30 minutes, or until the meat is tender.
Remove the pan from the heat and allow to cool. Once cooled, remove the ham hock, trotters and pig's ears from the pan. Pick all the meat from the ham hock and the trotters and set aside in a bowl.
Place the ears in between two oven trays and flatten, placing a heavy weight on top.
For the crubeens, heat the grapeseed oil in a pan and gently sweat the carrot, shallot and celeriac for 10-12 minutes, or until softened. Mix in the parsley, cornichons, mustard and white wine, then stir in the picked ham hock and trotter meat. Season, to taste, with salt and freshly ground black pepper.
Lay a sheet of cling film on the work surface and lay over half of the meat mixture in a row. Tightly roll up into a cylinder, twisting the ends of the cling film to seal, then place into the freezer for 30 minutes.
Tightly pack the remaining meat mixture into a 17cm x 11cm/6.5in x 4in terrine mould or loaf tin and chill in the fridge for at least one hour, or until set.
For the egg mayonnaise, place the chopped eggs into a food processor along with the mustard and vinegar. Blend, gradually adding the sunflower oil, until the mixture is smooth and thick.
Transfer the egg mixture into a bowl and stir in the cornichons, capers, parsley and caper berries. Season, to taste, with salt and freshly ground black pepper.
Remove the cylinder of crubeens from the freezer, remove the cling film and thinly slice. Arrange the slices on four serving plates, with some space between each slice, and allow to defrost to room temperature.
For the crisp pig's ears, place the flour into a large bowl and mix in a pinch of cayenne pepper. Cut the cooled and flattened pig's ears into thin slices and dust with the seasoned flour, then dip into the beaten egg and roll in the breadcrumbs.
Heat the vegetable oil in a deep, heavy-based pan to 180C/350F. (CAUTION: hot oil can be dangerous. Do not leave unattended.) Fry the pig's ears, in batches, for 3-4 minutes, or until golden-brown and crisp. Remove with a slotted spoon and drain on kitchen paper. Keep the oil at 180C/350F.
Remove the crubeens mixture from the terrine mould and cut into 2cm/1in cubes. Dust with flour, then dip into the beaten egg and coat in the breadcrumbs. Fry in the oil for 3-4 minutes, or until golden-brown and crisp. Remove with a slotted spoon and drain on kitchen paper.
To serve, arrange the fried cubes of crubeens and the crisp pig's ears in between the slices of crubeens. Spoon over some of the egg mayonnaise.