Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish or similar-sized casserole dish.
In a large bowl, mix the cream of mushroom soup, sour cream, mayonnaise (if using), 1 ½ cups cheddar cheese, garlic powder, onion powder, salt, and pepper until smooth. Fold in the steamed broccoli.
Spread the mixture evenly into the prepared baking dish. Sprinkle the remaining ½ cup of cheddar cheese on top.
In a small bowl, combine crushed crackers with melted butter. Sprinkle over the casserole for a crunchy topping.
Bake for 25–30 minutes, or until hot and bubbly with a golden top.
Let cool slightly before serving. Serve as a side dish or even a vegetarian main course.