Preheat your oven to 350°F (175°C).
In a large pot, combine the diced chicken breast with chicken broth, cream of chicken soup, sour cream, garlic powder, onion powder, and dried thyme. Stir well to combine.
Add the frozen mixed vegetables and cooked pasta to the pot. Season with salt and pepper to taste.
Transfer the mixture to a 9x13 inch casserole dish and spread it evenly.
Top the casserole with shredded cheddar cheese evenly across the surface.
If you like a crunchy topping, sprinkle crushed saltine crackers over the cheese.
Cover the dish with aluminum foil and bake in the preheated oven for 30 minutes.
Remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden.
Let the casserole sit for 5-10 minutes before serving.