Preheat the oven to 400 degrees F.
In a medium bowl combine the yeast, 1/4 cup flour, sugar, and salt. Add the warm water and olive oil. Mix until the ingredients are well combined. Gradually work the rest of the flour into the dough until the dough is smooth and is just slightly sticky.
Let the dough rest for 10 to 15 minutes. Grease or spray with a non-stick cooking spray a 10-inch cast iron skillet. Place the dough in the skillet and with your fingertips spread the dough until the bottom of the skillet is cover and there is a edge around the side of the skillet.
Spread the top of the dough with the pizza sauce. Spread the Italian sausage and mushroom on top of the sauce. Sprinkle the Italian seasoning over top of the sausage and mushrooms. Sprinkle the mozzarella cheese on top of the pizza.
Place the pizza in the preheated oven and bake 22 to 25 minutes or until the edge of the pizza crust is golden brown and cheese is melted and lightly golden brown.