Bring a large pot of water to a gentle boil. Add the broccoli florets and cook for about three minutes. Drain them well and place them aside. The broccoli should stay slightly crisp and bright green.

Preheat your oven to 350 degrees Fahrenheit. Lightly grease a 9x13-inch baking dish with butter or cooking spray. Spread the cooked broccoli evenly across the bottom of the dish for the first layer.

Place the cooked chicken evenly over the broccoli. I like using rotisserie chicken because it saves time and adds extra flavor. Make sure the chicken covers the broccoli so every bite stays balanced.

In a large mixing bowl, combine cream of chicken soup, mayonnaise, sour cream, lemon juice, garlic powder, onion powder, and black pepper. Whisk everything until smooth and creamy. The sauce should look thick and rich.

Carefully spread the creamy sauce over the chicken and broccoli layers. Use a spoon to cover the entire casserole evenly. This step helps every bite stay moist and full of flavor.

Sprinkle the cheddar cheese and Parmesan cheese evenly across the top. The cheese creates a golden, bubbly layer while baking. My family always loves the crispy cheesy corners the most.

In a small bowl, mix the crushed buttery crackers with melted butter. Stir until the crumbs are coated evenly. Sprinkle the buttery crumbs over the cheese layer for extra crunch and texture.

Place the casserole into the preheated oven. Bake for about 35 minutes until the top becomes golden brown and the sauce bubbles around the edges. Let it rest for five minutes before serving.