Preheat your oven to 350°F (175°C).
Steam the broccoli until it’s just tender but still bright green. Set it aside to cool slightly.
If not already cooked, prepare the chicken by baking, boiling, or pan-searing. Once cooked, shred or dice the chicken into bite-sized pieces.
In a large mixing bowl, combine the cream of chicken soup, sour cream (or mayonnaise), lemon juice, garlic powder, paprika, salt, and pepper. Stir until everything is well blended.
Spread the steamed broccoli evenly across the bottom of a 9x13-inch baking dish.
Layer the cooked chicken over the broccoli.
Pour the creamy sauce mixture over the chicken and broccoli, spreading it evenly with a spoon or spatula.
Add Cheese and Topping:Sprinkle the shredded cheddar and grated Parmesan cheese over the casserole. In a small bowl, combine the crushed Ritz crackers or breadcrumbs with the melted butter, mixing until the crumbs are evenly coated. Sprinkle this mixture on top of the cheese layer.
Place the assembled casserole in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and the sauce is bubbling.
Let the casserole cool for a few minutes before serving. Serve Chicken Divan with a side of rice, pasta, or a simple salad.