Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the drained green beans, cream of mushroom soup, milk, soy sauce, garlic powder, and black pepper. Stir until well mixed.
Gently fold in 1 cup of the French fried onions and the shredded cheddar cheese, if using.
Pour the mixture into a greased 2-quart baking dish and spread it evenly.
Bake in the preheated oven for 25 minutes.
Remove from the oven and sprinkle the remaining 1/2 cup of French fried onions on top.
Return to the oven and bake for an additional 10-15 minutes, or until the onions are golden brown and the casserole is bubbly.
Let it cool for a few minutes before serving.