Preheat oven to 350°F. Cook pasta in heavily salted boiling water for 10 minutes. Drain, but do not rinse. Toss with 1 tbsp olive oil. Set aside.
In a large bowl, mix together garlic powder, sherry, sour cream, cream of mushroom and cream of chicken soups and chicken broth until well combined. Gently mix in the chopped chicken and cooked spaghetti, tossing to coat.
Pour evenly into a greased 13x9" pan coated with non-stick cooking spray or olive oil. Sprinkle mozzarella and parmesan cheeses evenly on top. Bake in preheated oven for 30 minutes or until casserole is hot and bubbly.
Video
Notes
I like to use 2 rotisserie chicken breasts to get 2-3 cups of meat. Remove skin and chop breast meat into bite size pieces.