Bring a pot of water to a boil, add pasta and salt the water.
While the water boils combine ricotta, Parmigiano, parsley and pepperoni in a large bowl and reserve.
Heat a large skillet over medium heat with extra-virgin olive oil, 2 turns of the pan. When the oil is hot, add the peppers, onions, garlic and mushrooms. Saute 6 to 8 minutes until tender and mushrooms are dark. Season the vegetables with salt and pepper. Stir in tomatoes and reduce heat to low.
Add a ladle of starchy cooking water to the ricotta just before you drain the pasta. Drain pasta then toss with ricotta and pepperoni mixture. Pour pasta into a flameproof baking dish and top evenly with peppers, onion and mushroom sauce. Top with a layer of mozzarella, oregano and red pepper flakes. Place under hot broiler and melt cheese until golden and bubbly. Remove and serve with crusty bread.