Preheat the oven to 400?F.
Combine the beans and 8 cups cold water in a large saucepan or soup pot and bring to a boil. Cover the pot and remove from the heat. Let sit for 1 hour. Drain the beans in a colander and discard the soaking liquid. Set the beans aside.
Meanwhile, heat the bacon fat in a large Dutch oven. Season the lamb with the salt and pepper and cook the lamb in batches until very brown on all sides, 8 to 10 minutes per batch. Using a slotted spoon, transfer the lamb to a bowl and set aside. Add the onions, celery, thyme, bay leaves, and Essence and cook, scraping up any browned bits from the bottom of the pan, until the vegetables are soft, 4 minutes. Add the garlic and cook for 2 minutes. Add the tomatoes and Chicken Stock and return the meat to the pot. Bring to a boil, reduce the heat to a simmer, and cook for 30 minutes.
Add the beans to the pot and continue cooking until the beans are tender but not mushy, 1 to 1 1/2 hours. The cooking liquid should be slightly thickened, just enough to coat the beans and lamb. (If the sauce seems too thin, remove the meat and beans with a slotted spoon and cook until the liquid has reduced and is slightly thickened. Alternatively, if the cooking liquid has reduced too much, add a bit of water.) Add the green onions and parsley, taste, and season if necessary with additional salt and pepper.
Transfer the bean mixture to a 9 x 13-inch casserole and top with the bread crumbs and Parmesan cheese. Drizzle the top with the olive oil and bake, uncovered, until the casserole is golden brown on top and bubbly around the edges, about 30 minutes. Serve warm.
Makes 8 to 10 servings