Creating Turkey Tetrazzini is simple if you follow these steps:

1. Cook the Pasta: In a large pot, cook the spaghetti or fettuccine according to package instructions. Drain and set aside.
2. Sauté the Vegetables: In a large skillet, melt the butter over medium heat. Add the diced onion and garlic, cooking until softened. Stir in the sliced mushrooms and cook until they are tender.
3. Make the Sauce: Sprinkle the flour over the sautéed vegetables and stir to combine. Gradually add the chicken broth, stirring constantly until the mixture is smooth and thickened. Pour in the heavy cream and mix well.
4. Add Seasonings: Stir in the salt, pepper, thyme, and paprika. Add the shredded turkey and frozen peas to the sauce, mixing until everything is well combined.
5. Combine with Pasta: In a large bowl, combine the cooked pasta with the turkey mixture. Mix in half of the cheddar cheese, stirring until evenly distributed.
6. Transfer to Baking Dish: Pour the pasta mixture into a greased 9×13-inch baking dish, spreading it evenly.
7. Top with Cheese and Breadcrumbs: Sprinkle the remaining cheddar cheese and Parmesan cheese over the top. Finally, add the breadcrumbs for a crunchy topping.
8. Bake: Preheat your oven to 350°F (175°C) and bake for 25-30 minutes, or until the top is golden brown and bubbly.
9. Garnish and Serve: After removing from the oven, let it sit for a few minutes. Garnish with chopped parsley before serving.

These steps will guide you in creating an incredible Turkey Tetrazzini that everyone will enjoy!