• Generously butter a 9-inch square baking dish and set it aside.

To Make the Polenta:

• Combine the milk, water and salt in a heavy medium saucepan and bring to a boil. Reduce the heat to simmer and very slowly sprinkle in the cornmeal, whisking continuously. Cook for 5 minutes or until the cornmeal mixture pulls away from the sides of the pot.
• Remove the pan from the heat and whisk in 1 1/2 tablespoons of butter and 2 tablespoons of Parmesan cheese. Set it aside as you prepare the filling, which only takes a few minutes.

To Make the Filling:

• Put 2 to 3 tablespoons of good quality olive oil into a sauté pan and heat it to medium. Add the red pepper and garlic and sauté them for a few minutes to cook the peppers. Then add in the cherry tomatoes and spinach. Add salt and freshly ground pepper to taste. Cook only until the spinach has wilted down.
• With a spatula, spread half the mixture into the prepared 9" baking dish.
• Top with the vegetable mixture and place the basil leaves on top of the vegetables. Sprinkle half of the grated mozzarella cheese on top. Spread the remaining polenta mixture over the vegetables, then sprinkle on the 2 tablespoons of Parmesan cheese. Dot the casserole with the remaining butter.
• Let the polenta sit at least 15 minutes, or cover and chill up to 24 hours. When ready to cook, preheat the oven to 400°F. Bake uncovered for 30 minutes, or until golden brown and bubbly.
• Crack more black pepper over the top of the baked polenta before serving if you wish.
• Makes 4 servings.