Step 1

Preheat the oven to 350 degrees. Spray a 9 by 13 inch baking dish with cooking spray and set aside.

Step 2

Bring a large pot of water to a boil. Season the water with 1 teaspoon of salt. Add the spaghetti and cook according to package instrucitons.

Step 3

While the noodles are cooking, melt butter in a large skillet. Add the mushrooms and saute until they are soft, about 4 to 6 minutes.

Step 4

Whisk in the flour and then very slowly whisk in the chicken stock. Add just a few tablespoons at a time, whisking to combine it, until it is completely added.

Step 5

Whisk in the milk, garlic powder, onion powder, salt and pepper.

Step 6

Bring to a simmer, and then cook, stirring often, over low heat for 5 minutes. Stir in the sour cream and 1 cup mozzarella, taste and add more salt and pepper if needed.

Step 7

Add noodles and chicken to the prepared baking dish. Stir in the sauce. Top with remaining mozzarella and Parmesan cheese. Cover and bake for 30 minutes.