Throw cream of mushroom soup, all three green beans, and 1.5 boxes of crispy onions in a casserole dish. Mix.
Salt & pepper- more pepper. No, seriously. Add more pepper.
Then cover that shit and throw it in a preheated 350 oven. After about 30 minutes you can check on it, and then add the last ½ of the onions and uncover and bake an additional 10 minutes.