A parchment-lined baking sheet should be preheated to 450 degrees.
Place mushrooms with the tops down on a sheet tray prepared with olive oil and salt and pepper.
Put tomato sauce, Italian seasoning, cheese, and pepperoni on the pizzas, and then top them with cheese.
In a large baking dish, place the mushrooms, cheese, and basil, and bake for 10-12 minutes until the mushrooms are tender.