In a small bowl, combine the warm water, sugar, and active dry yeast. Stir gently and let sit for 5 to 10 minutes until foamy.
In a large mixing bowl, whisk together the flour, cornmeal, and salt.
Pour the yeast mixture and melted butter into the flour mixture. Stir with a wooden spoon until a dough forms.
Turn the dough onto a lightly floured surface and knead for about 7 to 10 minutes until smooth and elastic.
Place the dough in a lightly oiled bowl, cover with a clean kitchen towel, and let it rise in a warm place for 1 hour or until doubled in size.
While the dough rises, heat 1 tablespoon olive oil in a skillet over medium heat. Add the Italian sausage and cook, breaking it apart with a spoon, until browned and cooked through, about 7 minutes.
Add the chopped onion and minced garlic to the sausage and cook for another 3 to 4 minutes until softened.
Stir in the crushed tomatoes, dried oregano, dried basil, salt, and black pepper. Simmer the sauce over low heat for 20 minutes, stirring occasionally. Remove from heat and set aside.
Preheat the oven to 425°F (220°C).
Grease a 12-inch deep dish pizza pan or cast iron skillet with the remaining 1 tablespoon olive oil.
Punch down the risen dough and press it evenly into the bottom and up the sides of the prepared pan to form a thick crust.
Layer the shredded mozzarella cheese evenly over the dough.
Spread the sausage and tomato sauce mixture evenly over the cheese layer.
Sprinkle the grated Parmesan cheese over the top.
Bake the pizza in the preheated oven for 35 to 40 minutes, or until the crust is golden brown and the cheese is bubbly and slightly browned.
Remove the pizza from the oven and let it cool for 5 minutes.
Garnish with fresh basil leaves, slice, and serve hot.