Rub the salt over the pork, add the crushed garlic and thyme, rub in well.
Place the pork into a glass or porcelain dish, cover and leave overnight.
Following day, pre heat the oven to 160°C, Gas Mark 3.
Wash the salt off then place into a small deep baking tray, just big enough to fit the pork.
Gently heat the oil and pour carefully pour over the pork, so its submerged.
Cover and place the tray carefully into the oven to cook for about 2 hours or until a knife can pass through easily. The meat should be very soft, almost difficult top pick up, but not stringy and overcooked, Remove from oven and cool.
Lift out the cooked pork, place onto a flat tray skin side down and cover with cling film. Press with another tray and chill well.
When ready to cook, preheat the oven to 220°C gas 7.
Cut the pork into 6-8 perfect squares, trim off any ragged edges.
Place skin side down, into a hot, dry non-stick ovenproof frying pan and cook until the skin begins to crackle.
Transfer to the oven and cook for 15 minutes until heated through.
Meanwhile place the mayo, gherkins, onions and parsley together into a bowl and really mix well.
Add lemon juice and plenty of ground black pepper.