Creating Cheesy Broccoli Casserole is effortless if you follow these steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C).

2. Blanch the Broccoli: Bring a pot of water to a boil. Add the broccoli florets and cook for 2-3 minutes until bright green. Drain and set aside.

3. Prepare the Creamy Mixture: In a large mixing bowl, combine the sour cream, mayonnaise, chopped onion, garlic powder, salt, and black pepper. Mix well.

4. Add Broccoli and Cheese: Fold the blanched broccoli and shredded cheddar cheese into the creamy mixture until fully coated.

5. Transfer to a Baking Dish: Pour the casserole mixture into a greased 9×13-inch baking dish, spreading it evenly.

6. Prepare the Topping: In a separate bowl, combine the crushed butter crackers with melted butter and grated Parmesan cheese (if using). Mix until the crackers are coated.

7. Add Topping to Casserole: Evenly sprinkle the cracker mixture over the broccoli casserole.

8. Bake: Place the baking dish in the preheated oven and bake for 30-35 minutes, or until the top is golden brown and the cheese is bubbly.

9. Cool Slightly: Once baked, remove the casserole from the oven and allow it to cool for a few minutes before serving. This helps the casserole set up a bit more.

10. Serve and Enjoy: Cut yourself a hearty portion and enjoy this comforting dish!