A beautiful, well-browned crust is one of the glories of cassoulet, but how often the crust should be broken and pushed down into the cassoulet while it cooks is open to debate. Étienne Rousselot, owner of Hostellerie Étienne, whose recipe is adapted here, recommends breaking the crust often enough to keep the beans moist—at least four times. Others say that it should be broken every hour. We prefer to break the crust only as necessary (see steps 6 and 8). Rousselot defies Castelnaudary tradition by often using duck instead of goose; he finds it more tender. Cassoulet may be cooked for seven hours straight, but we prefer it cooked over two days.