Preheat oven to 350ºF.

Thaw out the frozen broccoli overnight. On a cutting board chop up the thawed broccoli florets into smaller pieces. There should be a variety of smaller chunks of and tiny ones.  Then dice half of a yellow onion. Set Aside.

In a large mixing bowl beat the 2 eggs. Then combine the melted butter, cream of mushroom soup, mayonnaise, salt, and pepper until well combined to make the sauce.  

Stir in the crispy fried onions and 2 cups of the taco shredded cheese, reserving 1 cup left to put on top later.

Pour the broccoli casserole batter into a 9 x 13 inch backing dish. Top with remaining 1 cup of the taco shredded cheese and finely crushed crackers.

Bake for 30 minutes uncovered or until top is golden.  Allow time to cool before serving.