Preheat your oven to 350°F and grease a 9x13-inch baking dish.
Microwave or boil the frozen broccoli until tender. Drain very well to remove excess water.
In a large bowl, gently combine the drained broccoli, garlic powder, salt, black pepper, onion powder, cream of mushroom soup, light mayonnaise, Greek yogurt, 1/2 cup of the cheddar cheese, and the beaten egg.
Pour the mixture into your prepared baking dish and sprinkle the remaining 1/2 cup cheddar cheese evenly on top.
In a small bowl, mix the crushed Ritz crackers with the Parmesan and melted butter. Sprinkle this topping evenly over the cheese.
Bake in the preheated oven for about 30 minutes until the topping is golden brown and the casserole is bubbly. If the top of the casserole becomes dark too quickly, cover the dish with foil and continue cooking until thoroughly heated.