Make the dough: Pour water into the bowl of a stand mixer fitted with a paddle attachment. Sprinkle in yeast and let dissolve, about 10 minutes. Add olive oil, melted butter, sugar, salt, cornmeal, and most of the flour, in that order. Knead, stopping occasionally to scrape down the sides and adding more flour as needed, until smooth and elastic.

Transfer dough to a lightly floured work surface. Knead in extra flour if needed. Roll into a ball and transfer to a bowl greased with ½ teaspoon olive oil. Cover with a plate and let rise in a warm spot until doubled in volume, 1 to 2 hours.

While the dough is rising, simmer pizza sauce in a pot over low heat until very thick, 60 to 90 minutes.

Preheat the oven to 425 degrees F (220 degrees C).

Poke dough to deflate and turn out onto your work surface. Press and stretch out dough into a round shape 3 to 4 inches larger than a 12-inch cast iron skillet. Brush the skillet with 1 ½ teaspoons olive oil. Place dough into the skillet; stretch and pull to evenly distribute it over the bottom and sides.

Apply fillings and toppings in order as follows: Lay provolone cheese over the bottom of the crust. Scatter fresh mozzarella over provolone, then add Italian sausage and firm mozzarella. Ladle pizza sauce generously over top. Grate Parmesan cheese over pizza sauce, then fold the crust edges in towards the center to seal in the sides. Drizzle 1 tablespoon olive oil over crust and center of pizza.

Bake in the center of the preheated oven until crust sounds hollow when tapped and pizza is beautifully browned, about 35 minutes. Let rest for 10 minutes before slicing.