Creating Easy Chicken Tetrazzini is a breeze if you follow these simple steps:

1. Cook the Pasta: In a large pot, cook the linguine or spaghetti according to package instructions until al dente. Drain and set aside.
2. Sauté the Vegetables: In a large skillet, melt the butter over medium heat. Add the sliced mushrooms and cook until tender, about 5 minutes.
3. Make the Sauce: Sprinkle the flour over the mushrooms and stir well. Gradually add the chicken broth while stirring continuously to avoid lumps. Cook for about 2 minutes until the mixture thickens.
4. Add Cream: Pour in the heavy cream and stir until well combined. Add garlic powder, onion powder, salt, and pepper. Cook for an additional 2-3 minutes until heated through.
5. Combine Ingredients: In a large mixing bowl, combine the cooked pasta, chicken, frozen peas, and the creamy sauce. Stir until all ingredients are well coated.
6. Transfer to Baking Dish: Pour the mixture into a greased 9×13-inch baking dish. Spread it evenly.
7. Top with Cheese: Sprinkle the shredded cheddar and grated Parmesan cheese evenly over the top.
8. Bake: Preheat your oven to 350°F (175°C) and bake for 20-25 minutes or until the cheese is bubbly and golden.
9. Garnish: Remove from the oven and let it cool for a few minutes. Garnish with fresh parsley before serving.

By following these steps, you will create an incredible Easy Chicken Tetrazzini that is sure to satisfy your taste buds and impress your guests.