If it were up to me, I'd have this creamy dish all the time.

Preheat your oven to 350°F (175°C).
Cook the linguine according to package instructions until al dente. Drain and set aside.
In a large skillet, melt the butter over medium heat. Add the chopped onion and sliced mushrooms, cooking until the onion is translucent and the mushrooms are tender, about 5 minutes.
Stir in the cream of chicken soup, sour cream, and chicken broth. Add the garlic powder, salt, and pepper. Mix well until the sauce is smooth and creamy.
Add the cooked chicken and linguine to the skillet, tossing to coat everything evenly with the sauce.
Transfer the mixture to a greased 9x13 inch baking dish. Sprinkle the Parmesan and mozzarella cheeses evenly over the top.
Bake in the preheated oven for 25-30 minutes, or until the cheese is melted and bubbly.
Garnish with chopped parsley before serving, if desired.
Variations & Tips
For a bit of a kick, add a pinch of red pepper flakes to the sauce. You can also substitute the chicken with turkey, making it a great way to use up holiday leftovers. If you prefer a lighter version, use low-fat sour cream and reduced-fat cheeses. For a more colorful dish, add some frozen peas or chopped bell peppers to the mix.