Heat the oil in a large skillet over medium heat. Add the onion, mushrooms and celery. Cook until the vegetables are tender, stirring occasionally. Add the garlic (if using) and cook for 1 minute. Remove from the heat.
Step 2
Heat the butter in an oven safe skillet over medium heat. Stir in the flour. Gradually stir in the heavy cream and vegetable broth. Cook and stir until the mixture boils and thickens.
Step 3
Add the turkey, onion and mushroom mixture, frozen carrots, peas and parsley.
Add the cooked spaghetti and cheese, tossing to coat. Season with salt and pepper, to taste.
Step 4
Heat the broiler. Combine the topping and sprinkle evenly over the pasta. Broil 4 inches from the heat (make sure you pan is oven safe AND that you use a pot holder to remove it!) until the turkey mixture is hot and bubbling with a golden brown top.