Make the bean stew: Soak the beans overnight in enough cold water to cover them well. Drain, rinse, and pick through them for stones and damaged beans. In a large saucepan, cover the pig’s foot or ham hock, pork belly or pancetta, and pork rind with cold water. Bring to a boil, simmer for 3 minutes, drain, and rinse in cold water. Reserve. In a large saucepan, cover the beans with lukewarm water. Bring to a boil, drain, and return to the pan. Cover with hot water. Add the carrots, onion, tomato, celery, garlic, and herb bouquet. Bring to a boil, add the reserved pig’s foot or ham hock, pork belly or pancetta, and pork rind. Simmer, covered, for 1-1/2 hours, until completely tender (don’t add salt yet). Transfer to a large pan to cool and reserve the beans in their cooking liquid. Remove the carrot, onion, and herb bouquet; discard. Taste and season with salt and pepper as needed, but be prudent, as the pork parts add a good bit of salty flavor.
Meanwhile, make the lamb stew: Cut the lamb into 2-1/2-inch pieces. Season with salt and pepper. In a large, heavy sauté pan over medium-high heat, melt the duck fat or heat the oil. Sear the lamb pieces until well browned on all sides. Remove with a slotted spoon and reserve. Add the carrot and onion, lower the heat to medium, and cover the pan. Sweat the vegetables until tender but not browned, about 6 minutes. Raise the heat, add the white wine, and boil, scraping up any browned bits with a wooden spoon, until the liquid is reduced by half. Add the reserved lamb and any juices, the tomatoes, herb bouquet, garlic, and broth or stock. Bring to a boil and then reduce the heat and simmer, covered, until the lamb is tender, about 1 hour, skimming off the fat and froth as needed. Discard the herb bouquet and reserve the lamb stew until it’s time to assemble the cassoulet.
Assemble the cassoulet: Heat the oven to 250°F. In a medium-size sauté pan over medium-high heat, heat half of the duck fat or olive oil. Add the sausage and brown it on all sides. When cool enough to handle, cut it into six pieces.
Cut the duck confit legs in half at the joint. Rub the garlic clove over the inside of an earthenware casserole, an enameled cast-iron Dutch oven, or a large ceramic soufflé mold. Retrieve the pig’s foot or ham hock, pork rind, and pork belly or pancetta from the bean stew. Discard the pig’s foot or ham hock bones. (If you’ve used a ham hock, tear off any remaining meat and add it to the bean stew.) Cut the pork belly or pancetta into 1/2-inch pieces and reserve. Cut the pork rind into 1/2-inch pieces and scatter them over the bottom of the dish.
With a slotted spoon, transfer one-third of the beans to the dish. Do the same with half the pork belly or pancetta, all of the duck confit, half the lamb stew (again, use a slotted spoon, because you’ll be using the cooking liquid later), and all of the sausage. Cover the meats with another one-third of beans, the remaining pork belly and lamb stew, and finish with the last one-third of beans. Combine the bean juices with the lamb sauce, taste for seasoning (remembering that the duck confit is salty), and pour just enough over the dish to barely cover the beans.
Sprinkle the dish with the breadcrumbs and drizzle the remaining duck fat (melt it first if it’s still solid) or olive oil over the breadcrumbs. Bake for 2-1/2 hours and then raise the heat to 350°F and bake until the crust is a rich golden brown and the cassoulet is bubbling around the edges, about another 30 minutes. Check the cassoulet during baking -- if it’s getting too dry, add more broth or stock; if the crust is browning too quickly, cover it with foil. Let the cassoulet rest for at least 30 minutes before serving. Bring the entire dish to the table and serve each guest some crust, beans, and pieces of the different meats.