Preheat your oven to 350°F (175°C).

Bring a pot of salted water to a boil. Add the chopped broccoli and cook for about 3-4 minutes until tender but still vibrant. Drain and set aside.

In a large mixing bowl, combine cream of mushroom soup, mayonnaise, garlic powder, salt, and pepper. Stir until blended smoothly.

Fold the cooked broccoli and shredded cheddar cheese into the mixture gently.

Pour the mixture into a greased baking dish, spreading it out evenly and pressing down lightly.

In a small bowl, mix breadcrumbs with melted butter and sprinkle over the casserole.

Bake in the preheated oven for 25 to 30 minutes, or until the topping is golden brown and the cheese is bubbling.