Preheat Oven:
Preheat your oven to 350°F (175°C).
Prepare Green Beans:
If using fresh green beans, bring a large pot of water to a boil. Add the green beans and cook for 5 minutes, then drain and set aside.
Mix the Sauce:
In a mixing bowl, combine the cream of mushroom soup, milk, soy sauce, garlic powder, salt, and pepper. Stir until smooth.
Combine Ingredients:
Add the cooked (or canned) green beans to the sauce mixture and stir to coat. Mix in ½ cup of the crispy fried onions.
Assemble the Casserole:
Transfer the green bean mixture to a 9x13-inch baking dish and spread it out evenly.
Bake:
Bake the casserole in the preheated oven for 25 minutes.
Add Topping:
Sprinkle the remaining crispy fried onions over the top of the casserole. Return to the oven and bake for an additional 5–10 minutes, or until the onions are golden and crispy.
Serve:
Remove the casserole from the oven and let it sit for a few minutes before serving.