Preheat the oven to 400°. Butter the skillet and dust the bottom with cornmeal; set it aside. Brown the sausage in a skillet then add the mushrooms, onion, and peppers; season with salt and pepper if needed. Cook until softened.
In the bowl of a stand mixer, whisk together flour, cornmeal, sugar, salt, and yeast. Pour the olive oil and water into the dry blend. Work dough with hook attachments on medium speed until it comes together.
Keeping the same speed, add one tablespoon of butter at a time to the dough. Work the dough for 4 minutes after the last piece of butter.
Turn the dough out onto a lightly floured surface and roll out to a 12-14 inch round. Lift the dough onto the skillet. Be sure to press the dough into the pan bottom and sides to release air pockets. Brush the dough with melted butter.
Spread the cheese onto the crust. Top with the cooked sausage or whatever toppings you choose. Spread the sauce over the sausage and sprinkle with the grated parmesan. Bake for 25-30 minutes. Edges should golden brown.
Be sure to roll it to the shape of you pan. Rectangular baking dishes work just as well.
Butter the surface of the skillet and sprinkle about one tablespoon of yellow cornmeal onto the bottom.
If the side cook too quickly, you may want to place aluminum foil around the edges to prevent overcooking.