Preheat the oven to 375–400°F.

Steam frozen broccoli or blanch fresh broccoli, then drain very well and let cool completely.

In a large bowl, mix cheddar cheese soup, mayonnaise, and beaten eggs until smooth.

Stir in shredded cheese, chopped onion, salt, and pepper.

Grease a 9x13-inch baking dish.

Spread the cooked broccoli evenly in the dish.

Pour the cheese mixture over the broccoli and spread evenly.

Sprinkle additional shredded cheese over the top.

In a small bowl, mix crushed crackers with melted butter.

Spread the cracker mixture evenly over the casserole.

Bake uncovered for 25–30 minutes, until golden brown and bubbly.

Let rest for 10–15 minutes before serving.