1. Soak the beans overnight in at least 2 litres cold water. You can use tinned beans but they will invariably end up either too mushy or undercooked in the finished dish; it really pays off to soak beans from dried. It’s not a weeknight dish anyway and if you cook a large batch you can easily freeze the surplus to reheat on a weeknight.
2. Drain the beans the next day and discard the water. Place them in a large pot with 2 litres of fresh water. Add the onion, the bouquet garni, the celery or leek and the pork belly rind, rolled and tied with string. Bring the beans to the boil, turn the heat down and simmer them for an hour, skimming the foam off the surface a couple of times. Drain, discard the herbs, onion and rind and keep to one side.
3. While the beans are cooking, preheat the oven to 220C/450F/gas 7. Prick the skin on the duck legs with a sharp knife, place them in a roasting tin (a disposable one will be a good idea) and roast for 40 minutes. Leave in the tin to cool. Turn the oven down to 140C/275F/gas 2.
4. Heat up a cast iron casserole over medium heat. If you haven’t got an ovenproof casserole dish suited for the hob as well, do the frying in a skillet and warm up a casserole dish in the oven to transfer the ingredients into.
5. Pour about 2 tbsp. Of the fat rendered from the duck legs into the frying dish/skillet. Add the diced pork belly and fry for 3 minutes until seared and lightly browned. Remove to a plate (or the casserole waiting in the oven) with a slotted spoon. Add the pancetta or bacon, fry and remove when browned. Add the onion, carrots, celery and whole garlic cloves to the pan and sweat for 5 minutes until softened.
6. Turn up the heat and pour in the wine. Let it bubble up, then return all the meat into the dish (or pour and scrape the frying pan content into the oven casserole if using two dishes). Add the tomato purée, half the chopped parsley, the bunch of thyme tied with a piece of string, about 1 tsp of salt and ½ tsp black pepper. Add the beans with about 700ml of water – enough to cover them in the casserole. Bring it to the boil.
7. Pull the skin off the duck legs with a small knife; it won’t come off quite so easily as the meat is not cooked much. Discard the skin. Keep the fat in the dish. When the cassoulet is simmering, stick the legs in and bury them under the beans. Cover the dish with a lid and place in the oven for 2 hours.
8. Whiz the bread in a blender or food processor to coarse breadcrumbs.
9. Remove the dish from the oven and fish out the legs. Pull the meat off the bone – it will now be very tender – and return to the pan. Check for seasoning. Top up with water if it’s cooked off too much (beans are catching on the bottom) and bake uncovered for another hour. Check halfway through if the sauce is thickening to your liking. If too watery, sprinkle some of the breadcrumbs over the surface and return to the oven.
10. Heat up 2 tbsp of the duck fat in a small skillet (the rest can now go), add the breadcrumbs and the garlic and fry until pale golden and crisp, about 5 minutes. Stir in some chopped parsley and season well with salt and pepper.
11. Let the cassoulet stand for 15 minutes before serving in bowls, sprinkled with the breadcrumbs. If preparing it in advance, load ovenproof individual dishes with cooked cassoulet and bake in the oven until piping hot, sprinkling over the breadcrumbs for the last few minutes of baking.
12. Serve with lightly dressed green salad and crusty bread.