Classic green bean casserole with cream of mushroom soup and crispy fried onions is a vegetarian Thanksgiving family tradition. This beloved side dish has graced American holiday tables since the 1950s.
Preheat the oven to 350°F (175°C) with a rack in the center position.
Bring a large pot of salted water to a boil, add green beans, and blanch for 5 minutes until tender-crisp; immediately drain and rinse under cold water to stop cooking.
In a large mixing bowl, stir together cream of mushroom soup, milk, salt, pepper, and half of the crispy fried onions until well combined.
Add blanched green beans to the mixture and gently toss to coat evenly.
Transfer the mixture to a 2-quart baking dish, cover with foil, and bake for 25 minutes; uncover, sprinkle with remaining fried onions, and bake for an additional 10 minutes until golden and bubbling.