Melt the butter in a saucepan. Add the flour and cook over medium heat for 1 minute, stirring constantly. Gradually add the milk, whisking until the mixture comes to a boil. Reduce the heat and simmer gently for 2 or 3 minutes. Season with salt and pepper.
Cover and set aside off the heat.
Cook the pasta in boiling salted water until al dente. Drain. Set aside.
With the rack in the middle position, preheat the broiler.
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.
New life for leftover turkey or roast pork.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.