Preheat your oven to 350°F.
In a large mixing bowl, combine the drained green beans, cream of mushroom soup, milk, soy sauce, black pepper, and 1 cup of French fried onions. If using, add the shredded cheddar cheese and mix until well combined.
Transfer the mixture to a 1.5-quart baking dish and spread it evenly. Top with the remaining ½ cup of French fried onions.
Bake in the preheated oven for 25-30 minutes, or until the casserole is hot and bubbly. For a crispy topping, broil for an additional 2-3 minutes, watching closely to prevent burning.
Let the casserole cool for about 5 minutes before serving.