Here are some common mistakes to avoid when making Pastiera di Riso: - Not cooking the rice properly: It is essential to cook the rice in the milk until it is soft and has absorbed all the liquid. If the rice is too undercooked, the filling will be hard, and if it is overcooked, it will be too mushy. - Using low-quality ricotta cheese: The ricotta cheese is the main ingredient in the filling and should be of good quality. It is best to use fresh, whole-milk ricotta cheese that is not too watery.