Creating a delectable Broccoli Cheese Casserole is simple when you follow these straightforward steps:

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

2. Prepare the Broccoli: In a pot of boiling water, blanch the broccoli for about 2-3 minutes. Drain and set aside.

3. Mix the Base: In a large bowl, combine the cream of mushroom soup, mayonnaise, sour cream, garlic powder, and black pepper. Stir until well combined.

4. Add Cheese: Fold in the shredded cheddar and mozzarella cheese until evenly distributed.

5. Combine with Broccoli: Add the blanched broccoli to the mixture and stir gently to coat all the florets.

6. Optional Chicken: If you’re adding chicken, fold it into the broccoli mixture now.

7. Transfer to Baking Dish: Grease a 9×13-inch baking dish and pour the broccoli and cheese mixture into it, spreading it out evenly.

8. Prepare Topping: In a small bowl, mix the crushed Ritz crackers with melted butter. Sprinkle this mixture evenly over the casserole.

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

10. Cool and Serve: Remove the dish from the oven and let it cool for about 5-10 minutes before serving.

These uncomplicated steps will guide you in creating an irresistible Broccoli Cheese Casserole that everyone will enjoy.