Prepare the Casserole

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish.
2. Prepare Broccoli: If using fresh broccoli, steam or blanch it for about 3-4 minutes until tender. If using frozen, thaw and drain.
3. Combine Ingredients: In a large bowl, mix the cream of mushroom soup, sour cream, shredded cheddar cheese, Parmesan, salt, and pepper.
4. Add Broccoli: Fold the broccoli into the cheese mixture until well combined.
5. Transfer to Baking Dish: Pour the broccoli and cheese mixture into the prepared baking dish.

Make the Topping

1. Mix Topping: In a small bowl, combine the breadcrumbs (or crushed crackers) with the melted butter.
2. Sprinkle Topping: Evenly sprinkle the breadcrumb mixture over the casserole.

Bake

1. Bake: Bake the casserole in the preheated oven for 30-35 minutes or until bubbly and golden brown on top.
2. Cool Slightly: Let the casserole cool for about 5 minutes before serving.