In the pot used for cooking the pasta, brown the mushrooms, onion and hot pepper flakes in the oil. Season with salt and pepper. Add the tomatoes and garlic and cook, stirring frequently, until the tomatoes start to burst, 3 to 4 minutes. Add the béchamel, pasta, turkey and peas. Heat through and adjust the seasoning. Transfer to a 23 x 33-cm (9 x 13-inch) baking dish. Sprinkle with cheese and brown under the broiler.
