Wash the broccoli carefully and cut into small florets. Boil or steam the broccoli for several minutes until slightly tender. Avoid overcooking because the broccoli continues baking later inside the casserole while absorbing the creamy sauce beautifully.

Preheat your oven to 350°F or 175°C before assembling the casserole. Proper oven temperature helps the dish cook evenly while creating golden bubbly cheese topping. Preparing early also makes the cooking process smoother and easier later.

In a large bowl, combine cream of chicken soup, sour cream, mayonnaise, garlic powder, onion powder and black pepper. Whisk until smooth and creamy. This rich sauce creates the comforting flavor that makes chicken divan so popular and satisfying.

Spread the cooked broccoli evenly across the bottom of a greased baking dish. The broccoli forms the first delicious layer of the casserole. Keeping it evenly spread helps every serving contain balanced flavor, texture and creamy goodness throughout.

Place shredded or cubed cooked chicken evenly over the broccoli layer. Rotisserie chicken works wonderfully because it saves time and adds extra flavor. The tender chicken blends perfectly with the creamy sauce and cheesy topping during baking.

Pour the prepared creamy sauce evenly over the chicken and broccoli layers. Use a spoon or spatula to spread gently if needed. The sauce should coat everything well so every bite tastes creamy, savory and comforting after baking.

Sprinkle cheddar cheese and Parmesan cheese generously across the top. In a small bowl, combine breadcrumbs with melted butter and scatter over the cheese. This topping creates delicious golden crunch while the cheese melts beautifully underneath during baking.

Place the baking dish into the preheated oven and bake for about 30 to 35 minutes. The casserole should become hot and bubbly while the top turns golden brown. The creamy sauce thickens perfectly during baking for rich comforting texture.

Remove the casserole from the oven carefully and let it rest for several minutes before serving. Sprinkle fresh parsley on top for color and freshness. Serve warm while the cheese stays melted and creamy for the best comforting flavor.