If you're looking to go low-carb but still want hearty and delicious meals that will actually fill you up, this recipe is the ticket. The black beans give you all the protein you need in one meal, while the polenta is a starch that has fewer carbohydrates than either rice or pasta used in typical casseroles.
This recipe calls for the polenta to be cooked, but you can use the precooked variety if you can find it and are short on time. Of course, you can add other types of beans, such as kidney or garbanzo or swap them out altogether. Like many casserole recipes, you can add whatever you want to it.