Preheat oven to 400 degrees F.

Rub squash on both sides with grapeseed oil. Set on a small rimmed baking sheet sliced side down and cover tightly with foil. Bake 40 - 50 minutes or until squash is cooked through and easily mashed with a fork. (Be mindful of the steam plume when lifting foil to check on squash.) Squash can be made ahead and kept covered in the fridge until needed. When ready to use, scoop flesh out of the skin and mash with a fork. Reserve 1 cup.

If you've made squash ahead of time, heat oven to 400 degrees F, otherwise, just leave it on.

To make polenta, bring 2 cups water to a boil. Meanwhile, melt 1 tablespoon butter in a medium-sized saucepan over medium-high heat. Add polenta, stir to toast briefly, and then gradually whisk in boiling water and a 1/2 teaspoon sea salt. Stirring often, cook until mixture starts to bubble; then turn heat to medium-low and cook 10 minutes or until polenta has thickened.

Add 1 cup reserved mashed squash and stir until mixture is smooth.

Melt 2 tablespoons butter in a 9-inch skillet or other deep-sided ovenproof vessel. Pour in polenta and slide into the oven. Bake until polenta is golden on top and the edges are crisp and pulling away from the side of the pan, 50 - 60 minutes.

Meanwhile, make tomato sauce. In a medium-sized saucepan oven medium heat, melt remaining 2 tablespoons butter. Stir in shallots and sauté 5 - 7 minutes. Add vinegar, cook 2 minutes or so, and then fold in diced tomatoes, a pinch sea salt, bay leaves, and black pepper to taste. Bring to a gentle boil and then turn heat to low. Cook, stirring occasionally, until tomato sauce is quite thick, about 15 minutes. Fold in parsley, remove from heat, and set aside.

Once polenta's cooked, spoon tomato sauce onto the center, arrange mozzarella on top, and finish with parsley and black pepper. Bake in a 425-degree oven until cheese is melted and bubbly, 10 - 12 minutes. Cool briefly, slice, and serve.