Make the dough: combine flour, cornmeal, yeast, sugar, and salt. Add warm water, melted butter, and olive oil. Mix until a dough forms, then knead 4–5 minutes until smooth. Cover and rise 60–90 minutes until puffy.
Make the sauce: heat olive oil in a saucepan, add garlic 30 seconds. Stir in crushed tomatoes, tomato paste, oregano, basil, salt, pepper, and red pepper flakes. Simmer 10–15 minutes until thick.
Preheat oven to 425°F. Grease a 9–10 inch deep dish pan or cast iron skillet.
Press dough into the pan, covering the bottom and pushing up the sides.
Layer sliced mozzarella over the dough. Add sausage (and pepperoni/veggies if using).
Spoon sauce over the top and spread evenly. Sprinkle Parmesan over the sauce.
Bake 25–35 minutes until crust is golden and the top is bubbling. If edges brown too fast, tent with foil for the last 10 minutes.
Rest 15–20 minutes before slicing and serving.