Preheat the oven to 3500F.
In a large bowl, mix together the cream of mushroom soup, milk, and black pepper until well combined.
Add the drained green beans to the bowl and stir until the beans are evenly coated in the mushroom sauce.
Pour the green bean mixture into a 9x13 inch baking dish and spread it out in an even layer.
Sprinkle the crispy fried onions on top of the green bean mixture.
Bake for 25-30 minutes, or until the casserole is heated through and the fried onions are crispy and golden brown.
