Preheat the oven to 140°C.
Cut the duck legs in half to separate the thigh and drumstick.
Put beans into a large saucepan and cover with cold water. Bring to a simmer and cook for five minutes, skimming any scum that rises to the top. Drain the beans and rinse.
Place beans in a large cast-iron casserole dish with a tight-fitting lid. Add duck legs and the rest of the ingredients and stir well. Add enough water to just cover the meat, about three cups. Cover pot with lid and put in the oven for two hours.
Remove the lid and bake for three more hours. A nice crust should appear and the beans should be tender and the meat soft.
Place a duck thigh and drumstick and pancetta piece on each plate and top with beans.