Preheat Oven:
Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish.
Blanch Broccoli:
Bring a pot of water to a boil. Add broccoli florets and cook for 2–3 minutes until bright green and slightly tender. Drain and rinse with cold water to stop cooking.
Make the Casserole Mixture:
In a large bowl, combine cream of mushroom soup, sour cream, mayonnaise, 3/4 cup cheddar cheese, garlic powder, onion powder, salt, and pepper. Stir in the blanched broccoli until evenly coated.
Assemble the Casserole:
Pour the broccoli mixture into the prepared baking dish. Spread evenly.
Prepare the Topping:
In a small bowl, mix crushed crackers, melted butter, and Parmesan cheese (if using). Sprinkle evenly over the broccoli mixture. Top with remaining 1/4 cup cheddar cheese.
Bake:
Bake for 25–30 minutes, until the topping is golden and the casserole is bubbly.
Serve:
Let cool slightly before serving.