Heat the oven to 150°C/300°F/gas mark 3.
Start by heating the oil in a large heavy-based casserole set over a medium–high heat. Add the cured and fresh pork belly pieces and cook the meat for six to eight minutes, or until well browned on all sides.
Lift the pieces out of the pan using a spatula or slotted spoon and set aside. Add the leeks to the same pan, along with the sliced garlic, all the herbs and a little seasoning. Sweat the leeks gently for about 10 minutes, then return the browned pork pieces to the pan, sprinkle over the plain flour and stir well.
Cook for a further three to four minutes, then pour in the cider and stock and bring to a simmer. Stir well, then place a tight-fitting lid on the pan and place in the oven for two hours, until the pork is fork tender.
Meanwhile, set a large frying pan over a high heat and add the butter. When it’s bubbling, add the mushrooms, season them lightly and sauté, turning them regularly, for six to eight minutes, until cooked through. Set aside.
When the casserole is ready, remove it from the oven and add the fried mushrooms and double cream. Stir well, then return the pan to the oven for 15 minutes without its lid.
Stir in the chopped parsley and check the seasoning before bringing to the table with a sharply dressed green salad and some good bread.