DOUGH: Dissolve yeast in the half cup warm water. Add the sugar and stir well. Set aside. In a large mixing bowl, combine 3.5 cups of flour, salt and cornmeal. Make a well in the center of the flour. Add the yeast mixture, the vegetable oil, and the half cup of water. Stir and mix thoroughly until the dough cleans the sides of the bowl and a rough mass is formed. Turn the dough out of the bowl onto a well-floured work surface. Knead and pound the dough (dust with flour if dough sticks to hands) for 5-6 minutes, until it is smooth and soft. Dust the dough and a large mixing bowl lightly with flour. Place the dough in the bowl and cover the bowl with plastic wrap and a kitchen towel. Let rise in a warm place until doubled in bulk, about 1.5 hrs.
After the dough has doubled, turn it out of the bowl and knead for about 2 minutes. Oil the bottom and sides round deep dish pizza pan. Spread the dough in the pan with your fingers and palm. (It will spread more easily if you let it sit in the pan for about 10 min.) Work the dough until it covers the bottom of the pan. Pull the edges of the dough up to form a lip or a pronounced border around the pan. Preheat the oven to 475. Prick the dough bottom with a fork at 1 cm intervals. Let rise for 30 min. Parbake for exactly 4 min. Brush the crust with olive oil or butter.
TOPPING: In a bowl, combine the tomatoes, basil, oregano and salt.
ASSEMBLY: Lay the slices of mozzarella cheese evenly over the crust. Spoon the tomatoes over the cheese. Sprinkly the grated parmesan cheese over the tomatoes. Add italian sausage. Drizzle about 1 tablespoon olive oil on top.
Bake the pizza in a preheated 500 degree oven on the bottom oven rack for 5 minutes; move the pizza to an oven rack 2 levels above the lower rack and bake an additional 15 minutes, until crust is lightly browned and sausage is cooked through.