Adjust your oven rack to the lowest position, and preheat the oven to 425 degrees.
Place the turkey sausage in a large saute pan and cook over medium heat, breaking up the meat into small pieces. Add the mushrooms, onions, and peppers if using. Continue cooking this mixture until the meat is no longer pink, and the vegetables are softened and caramelized, about 10 minutes.
Prepare a 12-inch deep dish pizza pan by spraying well with cooking spray, and lightly dusting the bottom with cornmeal.
Stretch or roll out one pound of the dough to cover the bottom or the pan, and press up the sides a bit.
Lay shredded mozzarella cheese over dough in an even layer.
Layer cooked sausage, and any flat filling like sliced onions, mushrooms, or spinach over the cheese.
Sprinkle with basil and oregano
Stretch or roll out the second pound of dough, and gently place it on top of the pizza, pressing the sides into the bottom layer of dough, so that they are well sealed.
Bake pizza for 20 minutes or until top dough is hard and just starting to turn light golden on the sides, and bottom dough is firm and starting to crisp.
While pizza is baking, sauté minced garlic in olive oil in a small saucepan for about 30 seconds. Remove the pan from the heat and add canned tomatoes. Stir to combine, and let simmer for 15 minutes to thicken.
Season with salt to taste.
Remove pizza from the oven, and reduce oven temperature to 375 degrees.
Spoon tomato-garlic mixture over the top of the pizza evenly, and return to oven for another 15-20 minutes, or until bottom crust is crispy and light brown.
Let pizza stand for 15 minutes before cutting. If desired, sprinkle grated parmesan cheese on top before serving.