Preheat oven to 350°F (175°C).
In a medium bowl, stir together the soup, milk, soy sauce (if using), and pepper until smooth.
Add the green beans and ⅔ cup of the fried onions. Mix well.
Transfer mixture to a 1½‑quart (1.5 L) casserole dish.
Bake uncovered for 25 minutes, until hot and bubbling.
Stir the casserole, then sprinkle the remaining fried onions evenly on top.
Bake for an additional 5 minutes, until the onions are golden brown.
Serve warm.