Preheat oven to 350°F.
In a large pot of boiling salted water, cook macaroni according to package directions. Drain and set aside.
In a large bowl, combine chicken, soup, mayo, sour cream, spinach, Swiss cheese, garlic powder, and thyme. Season with salt and pepper and stir to combine.
Stir macaroni into mixture then transfer to a 9x13-inch baking dish.
Sprinkle parmesan over casserole. Toss breadcrumbs and butter together and sprinkle over casserole.
Bake until golden brown and bubbly, about 40 minutes. Enjoy!
