It seems like it’s been around forever, but Campbell, the soup company, created the green bean casserole in 1955. It was traditionally composed of cream of mushroom soup, green beans, and crispy fried onions. Even today, Campbell estimates that 40 percent of its annual sales of Cream of Mushroom Soup end up in this recipe. Variations include adding pesto or Alfredo sauce and topping the casserole with almonds.