In large mixer bowl combine2 cups of the flour, the yeast, and salt.
Stir in water, egg, and oil.
Beat at low speed of electric mixer for 1/2 minute, scraping sides of bowl.
Beat 3 minutes at high speed.
By hand, stir in enough of the remaining flour to make a moderately stiff dough.
Turn out onto floured surface and knead till smooth, about 5 minutes.
Place in a greased bowl, turning once.
Cover; let rise till double (about 1 hour).
Divide dough; place in two greased 9x9x2-inch baking pans or three 8x1 1/2-inch round baking pans (sprinkle bottoms of pans with cornmeal, if desired).
With well-oiled hands, pat dough out to fit pan, making a 1/2-inch rim around edges.
Cover; let rise 30 minutes.
In skillet cook sausage and chopped onion till meat is brown; drain.
Stir in tomato sauce, oregano, and dash pepper.
Simmer, covered, 10 minutes.
When dough has risen, spread with a thin layer of the meat mixture.
Arrange onion rings and mushrooms atop; sprinkle with mozzarella cheese.
Spoon remaining meat mixture over.
Bake at 425°for 25 minutes.
Arrange tomato slices and green pepper rings on pizzas; sprinkle with Parmesan cheese and basil.
Bake 5 to 10 minutes more.