Preheat Oven: Set your oven to 350°F (175°C) and lightly grease a 9×13-inch baking dish.
Layer Chicken and Broccoli: Arrange the cooked chicken and broccoli in the prepared baking dish.
Make the Sauce: In a saucepan over medium heat, melt the butter. Stir in the flour and cook for about a minute. Gradually whisk in the chicken broth and milk, and continue cooking until the sauce has thickened. Season with salt and pepper.
Add Cheese: Remove the sauce from heat and stir in the shredded cheddar cheese until it’s melted and the sauce is smooth.
Combine: Pour the creamy cheese sauce evenly over the chicken and broccoli in the baking dish.
Add Breadcrumbs: Sprinkle the bread crumbs over the top of the casserole.
Bake: Place the dish in the oven and bake for about 25 minutes, or until the casserole is bubbly and golden brown on top.
Serve: Let the Broccoli Chicken Divan cool for a few minutes before serving. Enjoy warm!