Preheat the oven to 350°F (175°C).
In a large bowl, whisk together the Condensed Cream of Mushroom Soup and the Whole Milk until smooth; stir in the Soy Sauce and Ground Black Pepper to taste.
If using canned or frozen beans, drain and pat dry, then fold the Cut Green Beans into the soup mixture until evenly coated.
Transfer the mixture to a 9x13-inch (or similar) casserole dish and spread it into an even layer.
Sprinkle about half of the French Fried Onions over the top to create a crunchy underlayer, then bake for 25–30 minutes until the casserole is bubbly around the edges.
Remove from the oven, top with the remaining French Fried Onions, and bake an additional 5 minutes (or until the onions are golden and crisp).
Let the casserole rest for 5 minutes before serving so it sets slightly and is easier to scoop.
