In a large saucepan, heat 1 ½ tablespoons of the olive oil. Add the pancetta and cook over moderate heat until the fat has been rendered, about 5 minutes. Add the onion and cook, stirring occasionally, until softened, about 7 minutes. Add the beans, thyme sprigs, water and stock and bring to a boil. Simmer over low heat, stirring and skimming occasionally, until the beans are al dente, about 1 hour.
Add the garlic cloves to the beans and simmer until the garlic is tender, about 15 minutes. Discard the thyme sprigs. Season the beans with salt and let cool to room temperature. Cover and refrigerate the saucepan overnight.
Preheat the oven to 350°. Rewarm the beans on the stove over moderate heat. Transfer the beans to a 2 1/2 - 3 quart deep casserole dish. Nestle the duck legs, garlic sausage and bacon into the beans. Bake for about 40 minutes, until the cassoulet is bubbling and all of the meats are hot. Remove from cassoulet from the oven: remove the duck legs, discard the skin, take the meat off the bones and shred it coarsely. Return the duck the cassoulet and let rest for 15 minutes.
In a skillet, heat the remaining 1 tablespoon of olive oil. Add the breadcrumbs and cook over moderately high heat, stirring, until browned and crisp, about 3 minutes. Sprinkle the breadcrumbs and the parsley over the cassoulet and serve.