Preheat oven to 375°F.
Cook and shred or cube the chicken breasts. Alternatively, shred a whole rotisserie chicken.
Place the chicken in a 9×13 baking dish or disposable aluminum pan and spread evenly.
Add both cans of soup and the sour cream directly to the pan. Mix together with the chicken until well combined.
Sprinkle poppy seeds generously over the mixture and season with salt, pepper, and garlic powder. Stir to incorporate.
Spread the mixture evenly in the pan.
Layer the shredded cheddar cheese evenly over the top.
Crush the butter crackers and spread them in an even layer over the cheese.
Cover tightly with aluminum foil.
Bake at 375°F for 45 minutes.
Note: If baking alongside another casserole at 350°F, bake uncovered for 1 hour.
Serve hot straight from the pan.
