Preheat your oven to 350°F (175°C) and lightly grease a 9x13-inch baking dish.
In a large mixing bowl, whisk together the condensed cream of mushroom soup, whole milk, soy sauce, black pepper, and minced garlic until the mixture is smooth and well combined.
Stir in 3/4 cup of the grated Parmesan cheese and all of the drained green beans, folding gently until the beans are evenly coated in the creamy sauce.
Transfer the green bean mixture to the prepared baking dish and spread it into an even layer.
Sprinkle the remaining 1/4 cup of Parmesan cheese evenly over the top, followed by half of the French-fried onions.
Bake uncovered for 25-30 minutes, or until the casserole is bubbling around the edges.
Remove the casserole from the oven and carefully top with the remaining French-fried onions.
Return the casserole to the oven and bake for 5 more minutes, or until the onions on top are golden brown and crispy.
