Remove the sausages from the sauce to a cutting board, slice, and set aside, along with the sauce.
Bring 2 quarts of water to a boil in a large pot over high heat, and add the sea salt and remaining 1 tablespoon of oil. Stir in the cornmeal, a little at a time, whisking constantly to prevent the formation of lumps. Cook for 5 minutes, until the polenta comes away from the sides of the saucepan. Turn the polenta out onto a clean wooden board and allow to cool. Once it is cool, cut it into strips, using butcher's twine or a very sharp knife.
Preheat the oven to 400 degrees F.
Cover the bottom of a 9 by 13-inch oven-proof casserole or baking dish with a layer of sauce. Add a layer of polenta slices, then a layer of cheese, a layer of mozzarella, and a layer of sliced sausage. Repeat the process until all the ingredients have been used, ending with a layer of cheese. Bake in the oven 25 minutes. Let sit 5 minutes before serving.
Basic Tomato Sauce:
This sauce holds 1 week in the refrigerator or up to 6 months in the freezer.
Yield: 4 cups