Preheat Oven:
Preheat your oven to 350°F (175°C).
Prepare the Green Beans:
If using fresh green beans, blanch them by boiling in salted water for 3-4 minutes, then transfer to an ice bath to stop the cooking. Drain and set aside. For canned green beans, simply drain and rinse.
Mix the Sauce:
In a large mixing bowl, combine the cream of mushroom soup, milk, soy sauce, black pepper, and minced garlic. Stir until everything is well blended.
Add Cheese and Beans:
Fold in the green beans and shredded cheddar cheese into the sauce mixture, making sure the green beans are evenly coated.
Assemble the Casserole:
Pour the mixture into a casserole dish. Spread it evenly across the dish. Sprinkle ½ cup of the crispy fried onions on top of the casserole.
Bake:
Place the casserole in the preheated oven and bake for 25 minutes, until bubbling and heated through.
Add Final Toppings:
After 25 minutes, remove the casserole from the oven. Sprinkle the remaining crispy fried onions and Parmesan cheese (if using) on top.
Finish Baking:
Return the casserole to the oven and bake for an additional 5-10 minutes, or until the onions are golden brown and crispy.
Serve:
Once baked, remove the casserole from the oven and let it rest for 5 minutes before serving.