Inside Out Pizza Casserole

Inside Out Pizza Casserole 1 tablespoon vegetable oil 1 pound bulk pork sausage 1 package (8 ounces) sliced mushrooms 1 large onion, chopped (about 1 cup) 1 1/2 cups Pizzeria Style Pizza Sauce (I use Prego) 4 ounces sliced pepperoni, coarsely chopped 2 cups shredded mozzarella cheese (about 8 ounces) 1/2 cup grated Parmesan cheese 1/2 of a 15-ounce package refrigerated pie crust (1 crust), at room temperature Heat the oven to 400°F. Heat the oil in a 10-inch skillet over medium-high heat. Add the sausage and cook until it's well browned, stirring often to separate meat. Pour off any fat. Add the mushrooms and onion and cook until they're tender. Stir the pizza sauce and pepperoni in the skillet and cook until the mixture is hot and bubbling. Remove the skillet from the heat and let cool slightly. Stir in the mozzarella and Parmesan cheeses. Spoon the mixture into a 2-quart casserole. Place the crust over the sausage mixture and crimp or flute the edges. Cut several slits in the crust. Bake for 30 minutes or until the crust is golden brown. Let the casserole stand for 10 minutes before serving. Cut the casserole into 6 slices.