The pizza begins with a simple, thick layer of dough (made with olive oil and cornmeal) that is laid into a deep round pan and pulled up the sides, then parbaked before the toppings are added to give it greater spring; the pan is generally oiled heavily in order to create a fried effect on the outside of the crust. The crust is covered with cheese (generally sliced mozarella) and covered with meats and/or vegetables such as Italian sausage (a Chicago staple), onions, and bell peppers. A sauce, usually uncooked, of crushed or pureed tomatoes is then added. Typically this is finished with a grated cheese blend.