Preheat the oven to 350 degrees
First, rough chop the frozen, thawed broccoli and add it to a medium-sized bowl.
Then add the chopped onion, can of soup, mayonnaise, egg, shredded cheddar cheese, salt, pepper and garlic powder.
Now, mix everything together until it's evenly combined and add the mixture to a baking dish.
Next, using a food processor, crush the Ritz crackers up until they resemble breadcrumbs.
Then melt the butter and stir it into the crackers until they are coated.
Now, top the casserole with the remaining shredded cheese and cracker topping.
Finally, bake it for about 30 minutes or until the topping is golden brown and the sides are hot and bubbly. Serve warm and enjoy!