Preheat the oven to 180C (350F) Gas 4. To prepare the pork you’ll need a heavy-based frying pan. Rub the pork belly all over with the jerk seasoning and add to the pan, fat side down. Cook for a few minutes until golden, then quickly sear on all sides to seal. Remove from the heat and leave to rest for about 5 minutes.
Pour the cider into a large jug with the chicken stock. Place the onion rings in a roasting tin and scatter with the garlic and thyme. Lay the rested pork belly on top and pour the cider mixture around the meat. Season to taste. Cover with foil and then braise for 2 1/2-3 hours until the pork is tender and completely soft. Remove foil.
Increase the heat of the oven to 220C (425F) Gas 7. Return the jerk pork belly to the oven and roast for another 20-25 minutes until lightly crispy and golden brown. Leave to rest.
Meanwhile, place the potatoes in a large pan of boiling water and bring to the boil. Cover and simmer for 12-15 minutes until tender, then drain well. Tip the cooked potatoes into a large bowl, and using the back of a fork, gently crush each potato until it just splits and then drizzle over the olive oil. Season and then mix carefully until all the oil has been absorbed.
Meanwhile, cook the peas in a separate pan of boiling salted water for 3-4 minutes until tender. Fold through the crushed potatoes, then season to taste. Arrange on plates with slices of Jerk pork belly. Serve at once with some hot pepper sauce if you like.