Bring a large pot of salted water to a boil. Add 2 cups of your chosen pasta, such as spaghetti or fettuccine, and cook until al dente according to package instructions. Drain and set aside.
Heat 2 tablespoons of olive oil in a large skillet over medium heat. Add 1 cup of sliced cooked mushrooms and sauté until tender and slightly golden, about 5 minutes. Remove from skillet and set aside.
In the same skillet, add the flour and stir constantly for 1-2 minutes to create a roux. Gradually whisk in the 1 cup of chicken broth and 1 cup of cream, ensuring there are no lumps. Cook over medium heat until the sauce thickens, about 5 minutes. Stir in garlic powder, onion powder, salt, and pepper.
In a large mixing bowl, combine the cooked pasta, shredded chicken, sautéed mushrooms, chopped green onions, and the creamy sauce. Mix well to coat everything evenly.
Stir in 1 cup shredded mozzarella, 1/2 cup grated Parmesan, and the optional chopped turkey bacon. The turkey bacon adds a smoky, crispy contrast that’s totally delicious but feel free to skip or substitute as you like.
Preheat your oven to 350°F (175°C). Transfer the pasta mixture to a greased 9x13 baking dish. Sprinkle a little extra mozzarella and Parmesan on top if you like a golden crust. Bake uncovered for 25-30 minutes, or until bubbly and golden on top.
Let the Baked Chicken Tetrazzini rest for 5 minutes before serving. This allows it to set slightly and makes it easier to portion. Garnish with additional chopped green onions or fresh herbs if desired.