Aunt Sandy's Broccoli Casserole

-preheat oven at 400 degrees -put both boxes of broccoli in a pot and boil until they are fully cooked -mix cheese, mayo, cream of mushroom soup, onion in a large bowl -when done, drain broccoli and put in the large bowl and mix well -put in a casserole dish -in a separate bowl, crush both rolls of ritz crackers -pour melted butter on the crushed crackers and mix -sprinkle cracker mixture on casserole mixture -bake for 45 minutes or until cheese is bubbling on the sides