Preheat the oven to 350 degrees Fahrenheit. Lightly grease a baking dish with butter or cooking spray to prevent the casserole from sticking while baking.

Bring water to a boil in a saucepan. Add broccoli florets and cook for three minutes until slightly tender but still bright green and fresh.

Spread cooked broccoli evenly across the baking dish. Add shredded chicken over the broccoli layer so every serving gets both ingredients evenly distributed.

In a mixing bowl, combine cream of chicken soup, sour cream, mayonnaise, garlic powder, onion powder and black pepper. Stir until smooth and creamy throughout.

Pour the creamy mixture evenly over the chicken and broccoli. Use a spoon or spatula to spread the sauce across the entire casserole dish.

Sprinkle cheddar cheese and Parmesan cheese evenly over the top. The cheese melts beautifully and creates a rich, creamy layer during baking time.

Mix crushed buttery crackers with melted butter inside a small bowl. Stir until the crumbs become coated and slightly moist for crispy topping texture.

Sprinkle the buttery cracker mixture evenly over the casserole. Cover the entire top layer so every bite gets a crunchy and golden topping.

Place the dish inside the oven and bake for about 35 minutes. The casserole should become bubbly, hot and lightly golden on top.

Remove the casserole carefully from the oven. Let it rest for five minutes before serving so the sauce thickens slightly and flavors settle nicely.