Preheat your oven to 350°F (175°C). This ensures the oven is fully heated and ready for baking when the casserole is assembled.
In a medium mixing bowl, stir together the condensed cream of mushroom soup, soy milk, soy sauce, and black pepper until the mixture is smooth and well-combined.
Add the thawed green beans and 2/3 cup of the French fried onions to the soup mixture. Gently fold everything together until the green beans are evenly coated.
Spoon the green bean mixture into an ungreased 1 1/2-quart casserole dish, spreading it into an even layer.
Bake uncovered for 25 minutes, or until the casserole is hot and bubbly around the edges.
Carefully remove the casserole from the oven and stir the mixture. Sprinkle the remaining 2/3 cup of French fried onions evenly over the top.
Return the casserole to the oven and bake for 5 more minutes, or until the onions on top are golden brown and crisp.
